Monday 2 September 2019

 

09:00-10:30 - Plenary Sessions - Amphi Lavoisier

Chairperson: Carlo Sirtori

09:00 Mo-Pl-1

Passion Extreme Light

Gerard MOUROU, École polytechnique, Palaiseau, France

09:45 Mo-Pl-2

Enlarging the frontiers of research in the IR/mm range using synchotron radiation

Pascale ROY, Synchotron Soleil, France

10:30-11:00 - Coffee Break

11:00-12:30 - Parallel sessions Mo-AM

11:00-12:30 - Mo-AM-1 - Gyrotron 1 - Amphi Lavoisier

Chairperson: Jinjun Feng

11:00 Mo-AM-1-1
THALES TH1507 140 GHz 1 MW CW Gyrotron For W7-X Stellarator
Alberto Leggieri¹; Stefano Alberti²; Konstantinos Avramidis³; Gunter Dammertz³; Volker Erckmann⁴; Gerd Gantenbein³; Jean-Philippe Hogge²; Stefan Illy³; Zisis Ioannidis³; John Jelonnek³; Jianbo Jin³; Heinrich Laqua⁴; Francois Legrand¹; Christophe Lievin¹; Rodolphe Marchesin¹; Ioannis Pagonakis³; Tomasz Rzesnicki³; Philippe Thouvenin¹; Manfred Thumm³; Robert Wolf^4
1Thales Microwave Imaging Sub-systems, France; ²Swiss Plasma Center, École Polytechnique Fédérale de Lausanne, Switzerland; ³IHM - Karlsruhe Institute of Technology, Germany; ⁴Max Planck Institute of Plasma Physics, Germany

The status of the THALES 140 GHz 1 MW CW industrial gyrotron program for the W7-X stellarator is discussed in this paper. The industrial design and performances are briefly discussed with a focus on the tube reliability and endurance. The TH1507 tubes are capable of 1 MW RF CW output power at 140 GHz up to 1800 s. Actually, 9 tubes are running to energize the ECRH of W7-X plant; they can operate with efficiencies up to 44 %. After more than 10 years operation, the 2nd prototype has been opened opened in order to investigate the main physical wear during operation of the tube. This analysis shows an excellent robustness of the tube. It provides a large confidence in the robustness of the future ITER and TCV Thales programs and the upstarting W7-X 1.5 MW tube upgrade

11:30 Mo-AM-1-2
High-efficiency, Long-pulse Operation Of MW-level Dual-frequency Gyrotron, 84/126GHz, For The TCV Tokamak
Stefano Alberti¹; Konstantinos Avramidis²; Andrea Bertinetti³; William Bin⁴; Jeremie Dubray¹; Damien Fasel¹; Saul Garavaglia⁴; Jeremy Genoud¹; Timothy Goodman¹; Jean-Philippe Hogge¹; Pierre-François Isoz¹; Pierre Lavanchy¹; François Legrand⁵; Blaise Marlétaz¹; Jonathan Masur¹; Alessandro Moro⁴; Ioannis Pagonakis²; Miguel Silva¹; Ugo Siravo¹; Matthieu Toussaint^1
1SPC/EPFL, Switzerland; ²IHM, Karlsruhe Institute of Technology, Germany; ³Politecnico Di Torino, Italy; ⁴Institute of Plasma Physics/CNR, Italy; ⁵MIS/Thales, France

The first unit of the dual-frequency gyrotron, 84-126GHz/1MW/2s, for the upgrade of the TCV ECH system has been delivered and is presently being commissioned. During a first phase, long-pulse operation (TRF>0.5s) has been achieved and powers in excess of 0.9MW/0.9s and 1MW/1.2s have been measured in the evacuated RF-load at the two frequencies, 84GHz (TE17,5 mode) and 126GHz (TE26,7 mode), respectively. Considering the different rf losses in the experimental setup, the power level generated in the gyrotron cavity is in excess of 1.1MW and 1.2MW, with a corresponding electronic efficiency of 35% and 36%. These values are in excellent agreement with the design parameters and would likely lead to a gyrotron total efficiency higher than 50% in case of implementation of a depressed collector. The gyrotron behavior is remarkably reliable and robust with the pulse length extension to 2s presently only limited by external auxiliary systems.

11:45 Mo-AM-1-3
DEMO-Relevant Gyrotron Research At KIT
Konstantinos Avramidis¹; Gaetano Aiello¹; Philipp Thomas Bruecker¹; Benjamin Ell¹; Thomas Franke²; Gerd Gantenbein¹; Giovanni Grossetti¹; Stefan Illy¹; Zisis Ioannidis¹; Jianbo Jin¹; Parth Kalaria¹; Alexander Marek¹; Ioannis Pagonakis¹; Sebastian Ruess¹; Tobias Ruess¹; Tomasz Rzesnicki¹; Theo Scherer¹; Martin Schmid¹; Dirk Strauss¹; Manfred Thumm¹; Minh Quang Tran³; Chuanren Wu¹; John Jelonnek^1
1Karlsruhe Institute Of Technology, Germany; ²EUROfusion Consortium, Germany; ³École Polytechnique Fédérale de Lausanne, Switzerland

The DEMO-relevant gyrotron research at Karlsruhe Institute of Technology is driven by the European concept for a demonstration fusion reactor (EU DEMO). This paper reports on the recent results of the theoretical and experimental studies towards the development of gyrotrons fulfilling the DEMO needs.

12:00 Mo-AM-1-4
Powerful Continuous-Wave Sub-Terahertz Large-Orbit Gyrotron
Yuriy Kalynov; Vladimir Manuilov; Aleksander Fiks; Nikolai Zavolsky
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

Coherent subterahertz radiation is achieved for the first time in the large-orbit gyrotron operating at a higher cyclotron harmonic in the continuous-wave generation regime. A stable generation is achieved in the case of operation at the third and the second cyclotron harmonics at frequencies of 0.394 THz and 0.267 THz with a radiation power of 0.37 kW and 0.9 kW, respectively.

12:15 Mo-AM-1-5
Megawatt-Power Dual Frequency Gyrotrons For Modern Fusion Facilities
Leonid Popov¹; Marina Agapova¹; Yury Belov¹; Alexey Chirkov³; Grigory Denisov²; Alexander Gnedenkov¹; Vladimir Ilin¹; Igor Kazansky¹; Ilya Khailov¹; Artem Kuzmin¹; Alexander Litvak²; Vladimir Malygin²; Evgeny Sokolov²; Vladimir Zapevalov²; Vadim Miasnikov¹; Mikhail Morozkin²; Alexander Lyubimov¹; Elena Soluyanova¹; Evgeny Tai¹; Sergey Usachev^1
1GYCOM Ltd, Russian Federation; ²Institute of Applied Physics, Russian Federation

Nearly 20 years ago demand had arisen in the world practice of plasma investigations with gyrotron usage - to have a source of long-pulse microwave radiation with step-tunable frequency at megawatt-power level. Transparency bands of typical modern 1.8-mm single disc diamond output windows are distant at step of ~35GHz. Attempts to build the reliable broad band output window unit capable to provide long-pulse gyrotron multi-frequency operation with much smaller steps has not succeeded yet. In the same time 10 dual-frequency 140/105GHz long-pulse gyrotrons using single disc diamond window successfully run now at megawatt-power level providing ECRH at ASDEX Upgrade and KSTAR facilities.

11:00-12:30 - Mo-AM-2 - Solid State 1 - Petit Amphi

Chairperson: Alexej Pashkin

11:00 Mo-AM-2-1
2D THz Spectroscopic Investigation Of Ballistic Conduction-band Electron Dynamics In InSb
Sarah Houver; Lucas Huber; Elsa Abreu; Matteo Savoini; Steven Johnson
ETH Zurich, Institute for Quantum Electronics, Switzerland

We follow the trajectory of the out-of-equilibrium electron population in low-bandgap semiconductor InSb, using reflective cross-polarized 2D THz time-domain spectroscopy. The 2D THz spectra show a set of distinct features at combinations of the plasma edge and vibration frequencies. We assign these features to electronic nonlinearities, using finite difference time domain simulations, and show that the nonlinear response in the first picoseconds is dominated by coherent ballistic motion of the electrons. We demonstrate that this technique can be used to investigate the landscape of the band curvature near the Γ-point such as anisotropic characteristics in the (100)-plane.

11:30 Mo-AM-2-2
Excitonic Terahertz Emission From Silicon At Steady-State Interband Photoexcitation
Alexey Zakhar'in; Alexander Andrianov
Ioffe Institute, Russian Federation

Converted to poster in the Tuesday Poster Session

11:45 Mo-AM-2-3
Background-free Spectroscopy Of Impurity Transitions In Semiconductors With A Continuous-wave Terahertz Photomixer Source
Martin Wienold¹; Sergey G. Pavlov¹; Nikolay V. Abrosimov²; Heinz-Wilhelm Hübers^1
1German Aerospace Center (DLR), Germany; ²Leibniz-Institut fuer Kristallzuechtung, Germany

We present a method for background-free spectroscopy of shallow impurity transitions in semiconductors with residual impurity concentrations. The method is based on a continuous wave terahertz photomixer source and a scheme for optically modulating the concentration of neutral impurities.

12:00 Mo-AM-2-4
Tunable Stokes Shift In Uniaxially Stressed Silicon With Shallow Donors
Roman Zhukavin¹; Sergey Pavlov²; Andreas Pohl³; Nikolay Abrosimov⁴; Helge Riemann⁴; Britta Redlich⁵; Heinz-Wilhelm Hübers²; Valery Shastin^1
1Institute for Physics of Microstructures, Russian Federation; ²Institute of Optical Sensor Systems, German Aerospace Center (DLR), Germany; ³Department of Physics, Humboldt-Universität zu Berlin, Germany; ⁴Leibniz-Institut für Kristallzüchtung, Germany; ⁵Radboud University Nijmegen, Institute for Molecules and Materials, FELIX Laboratory, Netherlands

Experimental investigations of THz emission from silicon (Si) doped by shallow donors under uniaxial stress along the [001] crystal axis upon selective intracenter excitation by an infrared free electron laser are presented. spectral dependences of Si output integral emission on the pump wavelength and Si laser output terahertz emission spectra have been analyzed. Two mechanisms of stimulated emission have been recognized as inversion-population-based lasing and stimulated Raman scattering. It is shown that uniaxial stress allows to control the Stokes shift and by this the output Raman emission frequency in the active medium. The obtained results demonstrate the feasibility of broad range THz tuning in doped silicon by means of uniaxial stress.

11:00-12:30 - Mo-AM-3 - Metrology - Room 269

Chairperson: François Simoens

11:00 Mo-AM-3-1
Metrology Of Complex Refractive Index For Solids In The Terahertz Regime Using Frequency Domain Spectroscopy
Steven Chick¹; Guy Matmon²; Ben Murdin¹; Mira Naftaly^3
1University of Surrey, Advanced Technology Institute, United Kingdom; ²Paul Scherrer Institute, Laboratory for Micro- and Nanotechnology, Switzerland; ³National Physical Laboratory, United Kingdom

We present a metrological study of a new technique for measuring the complex refractive indices of solids in the THz regime. The technique is widely applicable thanks to requiring only frequency-domain spectroscopy, and is shown to be capable of high accuracy reconstruction of the complex refractive index (RI) spectrum. We quantify the sensitivity to experimental imperfections such as noise, showing that the new technique is more robust than previous methods. We demonstrate the extraction of RI of crystalline Si between 2 -- 20 THz using this method, and comment on the capability to discriminate between absorption and scattering using only a power-transmission measurement.

11:30 Mo-AM-3-2
Comparison Of Waveguide And Free-Space Power Measurement In The Millimeter-Wave Range
Andreas Steiger; Mathias Kehrt; Rolf Judaschke
PTB, Germany

A comparison of waveguide-based and free-space power measurements was carried out in the millimeter-wave range at PTB. The measurements revealed good agreement at 100 GHz of both power scales within their uncertainties. This confirms the consistent realization of SI traceable electronic and photonic power measurements at the national metrology institute of Germany.

11:45 Mo-AM-3-3
Average-Power-Scaling Of Broadband THz Radiation To 50mW
Joachim Buldt; Michael Mueller; Henning Stark; Cesar Jauregui; Jens Limpert
Institute of Applied Physics, Germany

We present on power scaling of broadband THz radiation. By using the two-color gas plasma scheme driven by a state-of-the art, ultrafast, high-average-power fiber laser system an unprecedented to average power of 50 mW. The possibilities for further scaling are discussed.

12:00 Mo-AM-3-4
Nicolson-Ross-Weir Method Using 1-port Network Analyzer For MmW And THz Material Characterization
Seckin Sahin; Niru Nahar; Kubilay Sertel
The Ohio State University, ElectroScience Laboratory, United States

We present a simplified Nicolson-Ross-Weir (NRW) material characterization procedure that employs only a 1-port network analyzer for data collection. This approach is particularly attractive for mmW and THz applications, as it eliminates the need for costlier 2-port measurements which are required in the conventional NRW method. Using two successive calibrations of the measurement port, we calculate the 2-port response of the sample under test. We demonstrate our approach for the WR8.0 waveguide band using a multi-offset-short calibration method. The particular calibration also provides frequency regions of validity as a byproduct of the procedure. Subsequently, the conventional NRW analytic procedure is applied to extract material permittivity and permeability using 2 successive 1-port measurements.

12:15 Mo-AM-3-5
Terahertz Continuous Wave System For Measuring Sub-100-µ M-thick Samples Using Gouy Phase Shift Interferometry
Dahye Choi; Il-Min Lee; Kiwon Moon; Dong Woo Park; Kyung Hyun Park
Electronics and Telecommunications Research Institute (ETRI), Republic of Korea

Terahertz continuous wave (CW) system for measuring sub-100-µm-thick samples using Gouy phase shift interferometry is proposed and demonstrated. When the optical path difference (OPD) of the interferometer is zero, destructive interference pattern is produced. In this case, OPD change induced interference signal change is sensitively detected and can be predicted with calculation. By minimizing the difference between the measured and the calculated signal, thickness of a sample can be determined. Thicknesses of sub-100-?m-thick samples are determined with the 5 % accuracy at 625 GHz.

11:00 -12:30 - Mo-AM-4 - THz Detectors 1 - Room 162

Chairperson: Kaz Hirakawa

11:00 Mo-AM-4-1
A Photomultiplier Tube With Sensitivity In The Entire Terahertz- And Infrared Frequency Range
Simon Lehnskov Lange¹; Naoya Kawai²; Peter Uhd Jepsen^1
1Technical University of Denmark, Denmark; ²Hamamatsu Photonics K.K., Electron Tube Division, Toyooka factory, Japan

We present here for the first time a photomultiplier tube (PMT), which is sensitive to light in the entire terahertz (THz)- and infrared frequency range. The PMT consists of a meta-material-based photocathode and a dynode electron multiplier system kept under vacuum. The photocathode principle is based on ultrafast electron cold field emission (CFE). This principle makes the PMT sensitive to the electric field of the incident radiation. The PMT therefore gives direct access to a host of characteristics of the incident radiation such as polarization, absolute polarity and absolute peak electric field strength with few-ns time resolution.

11:30 Mo-AM-4-2
Plasmonic Nanocavities For High-Responsivity And Broadband Terahertz Detection
Nezih Yardimci; Deniz Turan; Semih Cakmakyapan; Mona Jarrahi
University of California - Los Angeles, United States

We present a high-responsivity and broadband photoconductive terahertz detector based on a plasmonic nanocavity, which enables high quantum efficiency and ultrafast operation without using short-carrier-lifetime substrates. We experimentally demonstrate that a terahertz time-domain spectroscopy setup employing the presented detector can offer 102 dB dynamic range over 0.1-4.5 THz.

11:45 Mo-AM-4-3
Efficient Terahertz Detection With Perfectly-Absorbing Metasurface
Lucy Hale¹; Tom Siday¹; Polina Vabishchevich²; Charles Harris²; Ting Luk²; John Reno²; Igal Brener²; Oleg Mitrofanov^1
1University College London, United Kingdom; ²Sandia National Laboratories, United States

We demonstrate a unique photoconductive design for terahertz (THz) detection based on a perfectly absorbing, all-dielectric metasurface. Our design exploits Mie resonances in electrically connected cubic resonators fabricated in low-temperature grown (LT) GaAs. Experimentally, the detector achieves very high contrast between ON/OFF conductivity states (10^7) whilst also requiring extremely low optical power for optimal operation (100 μW). We find that the Mie resonances dissipate sufficiently fast and maintain the detection bandwidth up to 3 THz.

12:00 Mo-AM-4-4
Grating-assisted Electro-optic Sampling For Enhanced THz Detection Efficiency.
Alexei Halpin¹; Wei Cui¹; Aidan W. Schiff-Kearn¹; Kashif Masud Awan²; Ksenia Dolgaleva³; Jean-Michel Menard^1
1University of Ottawa, Department of Physics, Canada; ²Stewart Blusson Quantum Matter Institute, University of British Columbia, Canada; ³University of Ottawa, University of Ottawa, School of Electrical Engineering and Computer Scie, Canada

The use of nonlinear crystals for detection of THz radiation using electro-optic sampling (EOS) is widespread. Phase-matching typically restricts the bandwidth and detection efficiency for EOS. Here we exploit nanofabrication techniques to etch phase-masks into a <110>-cut GaP crystal, to allow for phase-matched detection THz detection. Our method allows to nearly double the detection bandwidth for the chosen crystal thickness, while also increasing the EOS detection efficiency by approximately 40%. Our method can be easily extended to other nonlinear media, or more complex photonic structures, and is highly applicable for broadband high-sensitivity spectroscopy.

12:15 Mo-AM-4-5
Detection Of THz-waves Using The Photomixing Approach
Florin Lucian Constantin
Laboratoire PhLAM, CNRS UMR 8523, France

The quadratic response to the optical fields and the nonlinear electrical response of a LTG-GaAs photomixer are exploited for detection of THz-waves. The rectification and the heterodyne detection in the THz regime using the photomixing approach are theoretically and experimentally demonstrated.

12:30 Mo-AM-4-6
Development Of Multistage Terahertz Wave Parametric Detector
Hikaru Sakai; Kosuke Murate; Yunzhuo Guo; Kodo Kawase
Nagoya University, Japan

The quadratic response to the optical fields and the nonlinear electrical response of a LTG-GaAs photomixer are exploited for detection of THz-waves. The rectification and the heterodyne detection in the THz regime using the photomixing approach are theoretically and experimentally demonstrated.

11:00-12:30 - Mo-AM-5 - THz TDS 1 - Room 151

Chairperson: Guilhem Gallot

11:00 Mo-AM-5-1
Time-Domain Detection Of The Electric Field And Its Conjugate Variable In Ultrabroadband Electro-Optic Sampling
Philipp Sulzer; Kenichi Oguchi; Jeldrik Huster; Andreas Liehl; Cornelius Beckh; Alfred Leitenstorfer
University of Konstanz, Germany

We demonstrate unambiguous detection of the conjugate variable to the electric field in a time-domain experiment. The polarization change induced by nonlinear mixing of probe and multi-THz fields via the Pockels effect is examined concerning changes in ellipticity and tilting of the polarization ellipsoid. Spectrally resolved measurements yield crucial insights into how sum and difference frequency generation processes shape the electro-optic signal for different detection crystals. This approach enables precise, even simultaneous, measurement of the electric field and its conjugate variable by combinations of different phase biases (lambda/4 and lambda/2) and spectral filtering.

11:30 Mo-AM-5-2
SLD-driven Terahertz Cross-correlation Spectroscopy
Daniel Molter¹; Michael Kolano¹; Georg von Freymann^2
1Fraunhofer ITWM, Germany; ²Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Germany

Terahertz cross-correlation spectroscopy is a fascinating method to generate signals comparable to those of conventional time-domain spectroscopy but using continuous light. We demonstrate the use of a superluminescent diode to drive a cross-correlation spectroscopy system resulting in a truly continuous terahertz spectrum.

11:45 Mo-AM-5-3
Single-shot Detection Of Terahertz Waveforms Using Non-collinear Time-encoding Technique
Kenichi Izumi¹; Kohei Kawana¹; Masataka Kobayashi¹; Yusuke Arashida²; Jun Takeda¹; Ikufumi Katayama^1
1Yokohama National University, Yokohama National University, Japan; ²Tsukuba University, Japan

We have developed a new scheme for accurately measuring terahertz (THz) waveforms based on a single-shot method using non-collinear time-encoding technique. In this scheme, THz pulses were focused non-collinearly on a LiNbO3 plate with a Si prism coupler together with chirped sampling pulses, enabling us to spatially separate sum- and difference-frequency components from the detected signals. This new approach -- single-sideband detection of each component -- reduces the waveform distortion, and then improves the temporal resolution of the time-encoding technique.

12:00 Mo-AM-5-4
Jones Matrix Calibration And Determination Of The Precision Of Terahertz Time-domain Polarimetry Based On Spinning E-O Sampling Technique
Kuangyi Xu¹; M. Hassan Arbab^2
1Stony Brook University, United States; ²Stony Brook University, United States

We have developed a terahertz polarimetry system by applying frequency modulation to electro-optic detection. A hollow-shaft motor rotates the detector crystal and the modulated signal is read by a lock-in-type reading instrument. We characterize the precision of this system to be approximately 1.3 degrees. Furthermore, we calculate the Jones matrix of the optical components to calibrate the systematic error induced by them.

12:15 Mo-AM-5-5
Time-Resolved Optical Pump -THz Ellipsometer Probe Measurements
Bong Joo Kang¹; Gregory Gäumann¹; Premysl Marsik²; Christian Bernhard²; Thomas Feurer^1
1University of Bern, Switzerland; ²University of Fribourg, Switzerland

We present the first optical pump-THz ellipsometer probe setup together with proof of principle measurements carried out on an UHR-silicon wafer. The retrieved time-resolved dielectric properties of NIR-pumped silicon show good agreement with two temperature model simulations.

11:00-12:30 - Mo-AM-6 - QCL 1 - Room 101

Chairperson: Karl Unterrainer

11:00 Mo-AM-6-1
Sub-terahertz Quantum-cascade Laser Source Based On Difference-frequency Generation
Kazuue Fujita; Shohei Hayashi; Akio Ito; Masahiro Hitaka; Tatsuo Dougakiuchi; Tadataka Edamura
Hamamatsu Photonics K.K., Japan

Authors report a sub-terahertz monolithic semiconductor source based on a high power, long-wavelength quantum cascade laser. In order to obtain higher nonlinear susceptibility in the sub-terahertz frequency region, we design long wavelength dual-upper-state active region in which transition dipole moments are substantially increased. A fabricated device with distributed feedback grating produces nearly watt-level infrared output power, and as a result, it exhibits a peak output power of ~20 ÃZ¼W at room temperature, around a frequency of ~700 GHz. Besides, the device produces an output power of 103 ÃZ¼W at 110 K.

11:30 Mo-AM-6-2
High-quality N-type Ge/SiGe Multilayers For THz Quantum Cascade Laser
Monica De Seta¹; Michele Montanari¹; Chiara Ciano¹; Luca Persichetti¹; Luciana Di Gaspare¹; Michele Virgilio²; Giovanni Capellini³; Marvin Zoellner³; Oliver Skibitzki³; David Stark⁴; Giacomo Scalari⁴; Jerome Faist⁴; Douglas Paul⁵; Thomas Grange⁶; Stefan Birner⁶; Mario Scuderi⁷; Giuseppe Nicotra⁷; Oussama Moutanabbir⁸; Samik Mukherjee⁸; Leonetta Baldassarre⁹; Michele Ortolani^9
1Università Roma Tre Dipartimento di Scienze, Italy; ²Dipartimento di Fisica "E. Fermi", Università di Pisa, Italy; ³IHP-Leibniz-Instut für innovative Mikroelektronik, Germany; ⁴Institute for Quantum Electronics, ETH Zürich, Switzerland; ⁵School of Engineering, University of Glasgow, United Kingdom; ⁶nextnano GmbH, Germany; ⁷Istituto per la Microelettronica e Microsistemi (CNR-IMM), Italy; ⁸École Polytechnique de Montréal, Department of Engineering Physics, Canada; ⁹Dipartimento di Fisica Università La Sapienza, Dipartimento di Fisica, Italy

We investigate optical and structural properties of n-type Ge/SiGe coupled quantum well systems, to assess the growth capability with respect to QCL design requirements, carefully identified by means of a modelling based on the non-equilibrium Green function formalism.

11:45 Mo-AM-6-3
1.65 THz Spanning Homogeneous THz Quantum Cascade Laser: Comb Operation And Injection Locking
Andres Forrer; David Stark; Martin Franckié; Tudor Olariu; Mattias Beck; Jérôme Faist; Giacomo Scalari
ETH Zürich, Switzerland

A homogeneous THz Quantum Cascade Laser with emission spectra spanning over 1.65 THz in a bi-stable, voltage driven regime is presented. A nearly 1 THz emission spectrum in the stable regime showing a narrow electrical beatnote indicating frequency comb operation is observed. Such a narrow beatnote could then be injection locked to an external RF source with powers low as -55 dBm. Together with the low threshold current density of 115 A/cm-2 this design could lead to octave spanning THz QCL frequency combs.

12:00 Mo-AM-6-4
Si-based N-type THz Quantum Cascade Emitter
David Stark¹; Luca Persichetti²; Michele Montanari³; Chiara Ciano³; Luciana Di Gaspare²; Monica De Seta²; Marvin Zöllner⁴; Oliver Skibitzki⁴; Giovanni Capellini⁴; Michele Ortolani⁵; Leonetta Baldassarre⁶; Michele Virgilio⁷; Thomas Grange⁸; Stefan Birner⁸; Kirsty Rew⁹; Douglas Paul⁹; Jérôme Faist¹⁰; Giacomo Scalari^10
1ETH Zurich, Switzerland; ²Università di Roma Tre, Italy; ³Università di Roma Tre, Italy; ⁴IHP-Leibniz-Institut für innovative Mikroelektronik, Germany; ⁵Università di Roma "La Sapienza", Italy; ⁶Università di Roma "La Sapienza", Italy; ⁷Università di Pisa,, Italy; ⁸nextnano, Germany; ⁹University of Glasgow, United Kingdom; ¹⁰ETH Zurich, Switzerland

Employing electronic transitions in the conduction band of semiconductor heterostructures paves a way to integrate a light source into silicon-based technology. To date all electroluminescence demonstrations of Si-based heterostructures have been p-type using hole-hole transitions. In the pathway of realizing an n-type Ge/SiGe terahertz quantum cascade laser, we present electroluminescence measurements of quantum cascade structures with top diffraction gratings. The devices for surface emission have been fabricated out of a 4-well quantum cascade laser design with 30 periods. An optical signal was observed with a maximum between 8-9 meV and full width at half maximum of roughly 4 meV.

12:15 Mo-AM-2-6-5
Stabilizing A Terahertz Quantum-cascade Laser Using Near-infrared Optical Excitation
Tasmim Alam¹; Martin Wienold¹; Xiang Lü²; Lutz Schrottke²; Holger T. Grahn²; Heinz-Wilhelm Hübers^1
1German Aerospace Center (DLR), Germany; ²Paul-Drude-Institut für Festkörperelektronik, Germany

We demonstrate a technique to simultaneously stabilize the frequency and output power of a terahertz quantumcascade laser. The technique exploits frequency and power variations upon near-infrared excitation and does not require an external terahertz optical modulator. By locking the frequency to a molecular absorption line, we obtain a linewidth of about 260 kHz and root-mean-square power fluctuations as low as 0.03%.

11:00-12:30 - Mo-AM-7 - Gas Spectro. & Sensing 1 - Room 201

Chairperson: Olivier Pirali

09:00 Mo-AM-7-1
High-Precision Mid-Infrared Spectroscopy With A Widely Tuneable SI-Traceable Frequency-Comb-Stabilised QCL
Dang Bao An Tran¹; Rosa Santagata¹; Mathieu Manceau¹; Anne Cournol¹; Louis Lecordier¹; Berengere Argence¹; Olivier Lopez¹; Sean K Tokunaga¹; Fabrice Wiotte¹; Haniffe Mouhamad¹; Andrei Goncharov¹; Michel Abgrall²; Yann Le Coq²; Hector Alvarez-Martinez²; Rodolphe Le Targat²; Won Kiu Lee²; Dan Xu²; Paul-Eric Pottie²; Anne Amy-Klein¹; Benoit Darquie^1
1Laboratoire de Physique des Lasers, CNRS-Université Paris 13, France; ²LNE-SYRTE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, France

We report measurements of absolute frequencies of various polyatomic species around 10 µm, at level of accuracies ranging from 10 Hz to 10 kHz, using a widely tuneable SI-traceable optical frequency comb-stabilized quantum cascade laser.

11:30 Mo-AM-7-2
Gas Spectroscopy At 222 -- 270 GHz Based On SiGe BiCMOS Using A Multi-Pass Ring Cell
Nick Rothbart¹; Klaus Schmalz²; Heinz-Wilhelm Hübers^1
1German Aerospace Center (DLR), Germany; ²IHP - Leibniz-Institut für innovative Mikroelektronik, Germany

We present broadband gas spectroscopy based on SiGe BiCMOS technology. A bandwidth of about 222 -270 GHz is achieved by a combination of two frequency bands on single transmitter and receiver chips. The antennas of transmitter and receiver for both bands are closely placed on a single chip such that coupling into the same optical system can be realized. We coupled the beams into a compact custom-made multi-pass ring cell with an optical path length of 1.9 m. We demonstrate sensitive gas spectroscopy capabilities by a full bandwidth spectrum of methanol.

11:45 Mo-AM-7-3
Tabletop Terahertz Chemical Sensor For Breath Analysis And Analytical Gas Sensing
Ivan Medvedev¹; Daniel Tyree¹; Parker Huntington¹; Jennifer Holt²; Ajani Ross¹; Robert Schueler¹; Christopher Neese²; Douglas Petkie^3
1Wright State University, Department of Physics, United States; ²The Ohio State University, Department of Physics, United States; ³Worcester Polytechnic Institute, Department of Physics, United States

We report on the design and development of a tabletop THz chemicals sensor capable of detecting a wide range of volatile organic compounds with absolute specificity at a part per trillion (ppt) level of dilution. The system is capable of rapid detection of light volatile compounds and was designed for quantitative analytical gas chemical sensing with specific focus on diagnostic breath sensing

12:00 Mo-AM-7-4
An Integrated Photoacoustic Terahertz Gas Sensor
Mattias Verstuyft¹; Elias Akiki²; Benjamin Walter³; Marc Faucher²; Mathias Vanwolleghem²; Bart Kuyken^1
1Ghent University, Belgium; ²IEMN Lille, France; ³Vmicro, Belgium

An on-chip transducer of terahertz light, absorbed by a trace gas, to a mechanical motion using photoacoustics is proposed. The silicon chip confines light in an optical cavity, wherein an acousto-mechanical cavity is housed. The concentration of a trace gas can be determined from the amplitude of a membrane's motion. The simulations presented here predict a minimum detectable limit of 1 ppm of methanol for 1 mW of terahertz power.

12:15 Mo-AM-7-5
Broadband Terahertz Heterodyne Spectrometer Exploiting Synchrotron Radiation At Sub-megahertz Resolution
Gaël Mouret¹; Joan Turut²; Zachari Buchanan³; Olivier Pirali⁴; Marie Aline Martin-Drumel⁴; Pacale Roy⁵; Francis Hindle¹; Sophie Eliet-Barois²; Jean François Lampin^2
1Université du Littoral Côte d'Opale, France; ²Institut d'Electronique Microélectronique et Nanotechnologie (IEMN), CNRS, France; ³Department of Chemistry, University of California, United States; ⁴Institut des Sciences Moléculaires d'Orsay, CNRS, Univ. Paris-Sud, Université Paris-Saclay, France; ⁵SOLEIL synchrotron, France

A new spectrometer on the AILES beamline of the SOLEIL synchrotron facility to achieve sub-MHz resolution in the THz and far-IR regions is currently being developed. Thanks to a dedicated heterodyne detection by use of a new kind of molecular laser as local oscillator along with a Fast Fourier Transform Spectrometer, several pure rotation absorption lines of H2S and CH3OH around 1.073 THz have been recorded.

12:30-14:00 - Lunch

14:00-16:00 -  Parallel sessions Mo-PM1

14:00-16:00 - Mo-PM1-1 - Gyrotron 2 - Amphi Lavoisier

Chairperson: Stefano Alberti

14:00 Mo-PM1-1-1
Dynamics Of Multimode Gyrotron Locked By Quasi-Monochromatic External Signal
Yulia Novozhilova; Gregory Denisov; Vladimir Bakunin
Institute of Applied Physics RAS, Russian Federation

Oscillation regimes in a multimode gyrotron under the influence of quasi-monochromatic external signal with a frequency close to the operating mode frequency are studied. The calculations were performed for a powerful 170 GHz gyrotron developed at IAP RAS as a perspective prototype for ITER. The parameter regions were found where the frequency of operating mode is locked by external signal and follows the variations in the external signal frequency.

14:30 Mo-PM1-1-2
1.2 THz Second Harmonic Gyrotron With Selective Groove
Ilya Bandurkin; Alexey Fedotov; Andrey Fokin; Mikhail Glyavin; Alexey Luchinin; Ivan Osharin; Andrey Savilov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

A method of selective discrimination of spurious low-harmonic oscillations in gyrotron operating at a high cyclotron harmonic was experimentally demonstrated in a 1.2 THz second cyclotron harmonic tube at a very high transverse mode TE 58,13. The obtained results prove the feasibility and efficiency of the proposed method of mode selection in the THz frequency range, and may be used in the design of a THz CW gyrotron operating at the third cyclotron harmonic.

14:45 Mo-PM1-1-3
High Power Millimeter Waves Generated By An Overmoded Relativistic Cherenkov-type Oscillator
Jinchuan JU; Juntao HE; Xingjun GE; Junpu LING; Ting SHU
National University of Defense Technology, China

An overmoded relativistic Cherenkov-type high power millimeter wave generator operating in Ka-band has been investigated. The associated particle-in-cell (PIC) simulation and experimental results are presented in this paper. The relativistic electron beam with a peak current of 9.9 kA was generated by a pulsed power accelerator launched at a voltage of 605 kV. The relativistic electron beam was guided by an axial magnetic field of about 1 T and transported through the overmoded slow-wave structure. Typically in experiments, the millimeter wave power radiated in the far field was about 630 MW with a frequency of 32.1 GHz and a pulse width of about 10 ns. The radiation mode was well controlled to be quasi-TM01 mode.

15:00 Mo-PM1-1-4
Long-pulse High-efficiency Relativistic Cherenkov Oscillators At L- And S- Bands
Xingjun GE
College of Advanced Interdisciplinary Studies, National University of Defense Technology, China

This paper presents the mechanism and realization of the long-pulse high-efficiency relativistic Cherenkov oscillators operating at L- and S-bands. In simulation, microwaves centred at 1.53 GHz are generated, with power of 2.4 GW, and efficiency of 38%. By optimizing the scheme of electron beam collection, the phenomenon of pulse shortening is effectively suppressed. In the experiment, microwaves centred at 1.52 GHz are generated, with power of 2 GW, efficiency of 33% and pulse duration above 140 ns. Furthermore, an S-band relativistic Cherenkov oscillator is designed. In simulation, microwaves centred at 3.76 GHz are generated, with power of 3.2 GW, and efficiency of 34%. In the experiment, microwaves centered at 3.75 GHz are generated, with power of 2.5 GW, efficiency of 31%, repetition rate of 20 Hz and pulse duration above 110 ns. In the further experiment, a microwave with pulse duration above 200 ns is generated.

15:15 Mo-PM1-1-5
Mechanisms Of Submillimeter Wave Generation By Kiloampere REB In A Plasma Column With Strong Density Gradients
Andrey Arzhannikov; Vladimir Burmasov; Ivan Ivanov; Petr Kalinin; Sergey Kuznetsov; Maksim Makarov; Konstantin Mekler; Sergey Polosatkin; Andrey Rovenskikh; Denis Samtsov; Stanislav Sinitsky; Vasily Stepanov; Igor Timofeev
Budker Institute of nuclear physics SB RAS, Russian Federation

Project of powerful submillimeter wave generator based on intense interaction of a relativistic electron beam with a magnetized plasma is developed at BINP RAS in collaboration with NSU. In presented experiments, the beam with parameters 0.8 MeV/15 kA/6 ÃfÆ'Ã.½Ãfâ?sÃ,¼s is injected into a plasma column with the density ~ 1015 cm-3. Spectral composition of the emission from the plasma column is studied in the frequency band 0.1 -- 1 THz. In the analysis of the results of our studies we focus on the role of strong plasma density gradients in generation of sub-mm waves.

15:30 Mo-PM1-1-6
THz Cherenkov Oscillator With Surface-Radiating Modes
Eduard Khutoryan¹; Sergey Ponomarenko¹; Sergey Kishko¹; Yoshinori Tatematsu²; Seitaro Mitsudo²; Masahiko Tani²; Alexei Kuleshov^1
1O. Ya. Usikov Institute for Radiophysics and Electronics of NAS of Ukraine, Ukraine; ²Research Center for Development of Far-Infrared Region, Japan

In this paper, we present and discuss some operation modes arising in the oscillator with a sheet electron beam and a periodically modified grating. Special attention has been paid to the modes when surface plasmon polaritons are coupled to the radiating wave. The presented simulation results indicate high potential of the proposed oscillator for an efficient generation of THz radiation.

15:45 Mo-PM1-1-7
Simulation Of Secondary Electrons In A Megawatt-Class Gyrotron Collector With Voltage Depression And Magnetic Sweeping
Stephen Cauffman; Monica Blank; Philipp Borchard; Kevin Felch
CPI, United States

In megawatt-class gyrotrons, the residual energy of the electron beam must be dissipated in the collector without compromising the vacuum integrity of the device, necessitating the use of various methods for lowering the peak power density to acceptable levels. Secondary electron emission from the collector surface can redistribute the power deposition profile of the incident (primary) beam, which can either be beneficial or detrimental. Secondary electrons may also be re-accelerated toward the gyrotron body, and, if not magnetically reflected, may interfere with the operation of the interaction circuit. Here, simulations of a megawatt-class gyrotron collector, including the effects of voltage depression, magnetic sweeping, and secondary/reflected electrons, are presented, to assess the potential impact on gyrotron operation and longevity.

14:00-16:00 - Mo-PM1-2 - Solid State 2 - Petit Amphi

Chairperson: Christine Kadlec

14:00 Mo-PM1-2-1
Unveiling Temperature-Dependent Scattering Mechanisms In Semiconductor Nanowires Using Optical-Pump Terahertz-Probe Spectroscopy
Jessica Boland¹; Francesca Amaduzzi²; Sabrina Sterzl³; Heidi Potts²; Gözde Tütüncüoglu²; Laura Herz³; Anna Fontcuberta i Morral²; Michael Johnston^3
1University of Manchester, United Kingdom; ²École Polytechnique Fédérale de Lausanne, Switzerland; ³University of Oxford, United Kingdom

Optical-pump terahertz-probe (OPTP) spectroscopy is a powerful, non-contact tool for extracting the electrical conductivity within a material. In this work, we show how OPTP spectroscopy can be used to extract the temperature-dependent electron mobility and photoconductivity lifetime within semiconductor nanowires (NWs), in order to reveal the underlying scattering mechanisms governing carrier transport in these materials.

14:30 Mo-PM1-2-2
Time-Resolved THz Spectroscopy Of Metal-Halide Perovskite Single Crystals And Polycrystalline Thin Films
Chelsea Q. Xia¹; Qianqian Lin²; Jay B. Patel¹; Adam D. Wright¹; Timothy D. Crothers¹; Rebecca L. Milot³; Laura M. Herz¹; Michael B. Johnston^1
1University of Oxford, Clarendon Laboratory, United Kingdom; ²Wuhan University, School of Physics and Technology, Wuhan University, China; ³University of Warwick, Department of Physics, United Kingdom

In this study the photoconductivity and charge-carrier dynamics of the metal-halide perovskite MAPbI3 is investigated via optical-pump-THz-probe spectroscopy (OPTPS). We perform OPTPS on polycrystalline MAPbI3 thin films in both transmission and reflection modes, and demonstrate the consistency of extracted mobility and recombination parameters between the two geometries. Furthermore, we performed OPTP measurement on MAPbI3 single crystal in reflection and compare the mobility and charge recombination dynamics between the polycrystalline thin films and perovskite single crystals. Finally, the consequence of our results for future metal halide optoelectronic devices are discussed.

14:45 Mo-PM1-2-3
The Observation Of Spin Reorientation Phase Transition In Sm1-xErxFeO3
Yohei Koike; Kazumasa Hirota; Hongsong Qiu; Shodai Kimoto; Kosaku Kato; Masashi Yoshimura; Makoto Nakajima
Institute of Laser Engineering, Osaka University, Japan

Through the observation of magnetic resonance modes by terahertz time domain spectroscopy (THz-TDS) at the various temperature, we succeeded in observing spin reorientation phase transition (SRPT) which occurs at 310 K for Sm0.7Er0.3FeO3 single crystals. Furthermore, THz-pump and optical-Faraday-rotation measurement was introduced and the weak F-mode signals were successfully observed just below SRPT temperature.

15:00 Mo-PM1-2-4
Enhanced Generation Of THz Radiation In The Island Films Of Topological Insulators Bi2-xSbxTe3-ySey
Kirill Kuznetsov¹; Petr Kuznetsov²; Daniil Safronenkov¹; Alexey Temiryazev²; Galina Yakushcheva²; Galiya Kitaeva^1
1Lomonosov Moscow State University, Faculty of Physics, Russian Federation; ²Kotelnikov IRE RAS (Fryazino branch)

Using time-domain spectroscopy we studied the topological insulators, Bi2-xSbxTe3-ySey thin films of different thickness and chemical composition. The obtained temporal dependences of terahertz pulses show that generation of THz radiation is more effective in an island film with a total thickness of about tens of nanometers. For the first time an amplification of the THz radiation power by applying an external electric field to a topological insulator is demonstrated. This effect can be useful for fabricating photoconductive antennas based on topological insulators.

15:15 Mo-PM1-2-5
Analysis Of Glass Transition Temperatures In Indomethacin Polymer Mixtures
Adam Zaczek; Axel Zeitler
University of Cambridge, Department of Chemical Engineering and Biotechnology, United Kingdom

While drugs are typically created, stored, and administered in the more stable crystalline state, there is interest in industrial settings to stabilise amorphous pharmaceuticals to overcome bioavailability constraints. Terahertz time-domain spectroscopy (THz-TDS) can be used to determine how the glass transition temperatures directly relate to the stability of an amorphous sample. Indomethacin is an extensively studied anti-inflammatory, providing a benchmark sample for amorphous studies with terahertz spectroscopy. By mixing indomethacin with varying ratios of polymeric matrices, its amorphous stability can be increased, revealing trends in the THz-TDS results that directly relate to the potential energy surface of the system which provides insight into the interactions that occur within amorphous mixtures.

15:30 Mo-PM1-2-6
Coexistence Of Ferromagnetic And Superconducting Domains In Co-doped BaFe2As2 Superconductors Probed Using Infrared Faraday Measurements
Alok Mukherjee¹; Murat Arik¹; Jungryeol Seo¹; Hui Xing¹; Payam Taheri¹; Hao Zeng¹; Igor Mazin²; Hikaru Sato³; Hidenori Hiramatsu³; Hideo Hosono³; John Cerne^1
1University at Buffalo, Physics Dept., United States; ²Naval Research Laboratory, United States; ³Tokyo Institute of Technology, Japan

We explore the electronic and magnetic properties of superconducting iron pnictide films by probing their infrared Hall conductivity as a function of function of energy (0.1- 1.3 eV), temperature (10-300 K) and magnetic field (B = 0-7 T). We find hysteretic behavior in the complex infrared Faraday angle, θ_F, at low B over the entire temperature range. At higher B, θ_F is linear in B and we observe a peak in the high B-field slope near 50 K, which may be related to the superconducting Tc of the films.

15:45 Mo-PM1-2-7
THz Driven Dynamics In Mott Insulator GaTa4Se8
Elsa Abreu¹; Danylo Babich²; Etienne Janod²; Benoît Corraze²; Laurent Cario²; Steven Johnson^1
1ETH Zürich, Switzerland; ²Institut des Matériaux Jean Rouxel, Université de Nantes, France

GaTa4Se8 is a Mott insulator known to exhibit an electric Mott transition, characterized by a drop in electrical resistivity, when an electric field larger than 1 -- 10 kV/cm is applied for a few tens of microseconds using electrodes deposited on the sample. Here, we show that a resistivity drop can be induced in this material within less than a picosecond. These dynamics occur after excitation by a high field THz pump pulse and persist for a few picoseconds, well beyond the duration of the pump pulse.

14:00-16:00 - Mo-PM1-3 - Ultrafast - Room 269

Chairperson: Juliette Mangeney

14:00 Mo-PM1-3-1

Terahertz Pulse Trapping Beyond The Delay-Bandwidth Limit
Nima Chamanara¹; Lauren Gingras¹; Aidan W. Schiff-Kearn¹; Jean-Michel Ménard²; David G. Cooke^1
1McGill University, Canada; ²University of Ottawa, Canada

We demonstrate the trapping of a broadband THz pulse in a cavity with dynamic walls created faster than the cavity transit time. The trapping bandwidth and dwell time within the cavity, formed by patterned fs photoexcitation of reflective metallic regions within a silicon filled parallel plate waveguide, is shown to violate the delay-bandwidth limit of a passive resonator.

14:30 Mo-PM1-3-2
Ultrafast Metallization In NbO2 Studied By Pump-probe THz Spectroscopy
Rakesh Rana; J. Michael Klopf; Jörg Grenzer; Harald Schneider; Manfred Helm; Alexej Pashkin
Helmholtz-Zentrum Dresden-Rossendorf, Germany

Niobium dioxide (NbO2) is an isovalent counterpart of VO2 with a considerably higher transition temperature (TC = 1080 K). We have performed time-resolved optical pump -- THz probe measurements on a NbO2 epitaxial thin film at room temperature. Notably, the pump energy required for the switching into a metastable metallic state is smaller than the energy necessary for heating NbO2 up to Tc providing strong evidence for the non-thermal character of the photoinduced insulator-to-metal transition.

14:45 Mo-PM1-3-3
Ultrafast Dynamics Of Hydroxyl Radical Observed By Its FID Radiation In Magnetic Field
Vitaly Kubarev¹; Evgeniy Chesnokov²; Lev Krasnoperov³; Pavel Koshlyakov^2
1Budker Institute of Nuclear Physics, Russian Federation; ²Institute of Chemical Kinetics and Combustion, Russian Federation; ³New-Jersey Institute of Technology, United States

Ultrafast dynamics of OH radical was investigated by its Free Induction Decay (FID) signal. In our experiments doublet rotational line of the radical was excited by pulse of free-electron laser. Effect of a magnetic field on polarization of the FID was studied by numerical simulation. Experimental investigations of the magnetic field effect is in progress now.

15:00 Mo-PM1-3-4
Terahertz Spectroscopy To Unveil Intraband Scattering In Photoexcited Graphene
Srabani Kar¹; Stephanie Adeyemo¹; Ajay Sood²; Hannah Joyce^1
1University of Cambridge, United Kingdom; ²Indian Institute of Science, Department of Physics, India

Intraband scattering dynamics of optically excited graphene has been explored by using time resolved terahertz spectroscopy. The results for different forms of graphene in terms of layers, Fermi energy position, hydrogen functionalization have been discussed and explained by using Boltzmann transport theory. It is shown how the short-range and Coulomb scattering play important roles in determining photoinduced terahertz conductivity. Photoexcited bilayer graphene showed transition from negative to positive photo-induced terahertz conductivity in the spectral range 0.5-2.5 THz. It is revealed that short-range scattering plays the most significant role to determine the ultrafast photocondcutivity of graphene at terahertz range. However, at low doping state, Coulomb scattering contribute significantly to the imaginary part of conductivity.

15:15 Mo-PM1-3-5
Nonlinearity Of Ultrafast Anomalous Hall Currents In GaAs
Christoph Dresler; Mark Bieler
PTB-The National Metrology Institute of Germany, Germany

PTB-The National Metrology Institute of Germany, PTB-The National Metrology Institute of Germany, Bundesallee 100, Germany
We induce ultrafast anomalous Hall currents in GaAs by optical femtosecond excitation at various temperatures and magnetic fields. The currents' dynamics is studied by detecting the simultaneously emitted THz radiation. A linear behavior is obtained at room temperature and low magnetic fields. However, at higher magnetic fields and, in particular, at low temperatures, we enter a highly nonlinear regime, in which the current dynamics drastically varies. Most likely, this variation results from different microscopic mechanisms which compete against each other

15:30 Mo-PM1-3-6
THz Response Of Metallic Structures To Femtosecond Laser Pulses
Ivan Oladyshkin; Daniil Fadeev; Vyacheslav Mironov
Institute of Applied Physics of the Russian Academy of Sciences, Russian Federation

The talk is devoted to the nonlinear effects in metallic structures (like gratings and nanoparticle arrays) irradiated by intense femtosecond laser pulses. Possible mechanisms of delayed THz response and specific non-quadratic nonlinear regimes of conversion are analyzed. In contrast to previous models, only low-frequency currents inside the metal are considered without involving electron emission and acceleration. Special attention is paid to the role of plasmonic resonances at optical frequency in the enhancement of low-frequency nonlinear response.

15:45 Mo-PM1-3-7
Surface THz Emission From Germanium
Ignas Nevinskas; Ričardas Norkus; Arūnas Krotkus

Center for Physical Sciences and Technology, Lithuania

Terahertz emission from germanium after femtosecond laser pulse excitation is a result of the photo-Dember effect and the built-in surface electric field. The indirect band gap semiconductor is investigated with various excitation wavelengths and different dopant types to differentiate these mechanisms. THz pulse emission is observed even at exciting quanta energies lower than the direct band gap. The azimuthal angle dependences suggest a 3rd order optical nonlinearity.

14:00-16:00 - Mo-PM1-4 - 2D Materials 1 - Room 162

Chairperson: Berardi Sensale Rodriguez

14:00 Mo-PM1-4-1

THz Excited State Level Spacing In Encapsulated Graphene Quantum Dots
Elisa Riccardi; Sylvain Massabeau; Federico Valmorra; Michael Rosticher; Jerome Tignon; Takis Kontos; Sebastien Balibar; Sukhdeep Dhillon; Robson Ferreira; Juliette Mangeney
Laboratoire de Physique de l'Ecole Normale Superieure, France

We report a high-quality encapsulated graphene quantum dot that exhibits stable Coulomb diamonds and excited states with a spacing of 0.5 THz. The quantum dot is connected to a bow tie antenna for measurements under THz illumination. The experimental set-up includes a dilution cryostat operating at temperature T<200mK with optical access at THz frequencies.

14:30 Mo-PM1-4-2
PT-Symmetric Terahertz Photoconductivity In Hg1-xCdxTe
Dmitry Khokhlov¹; Akeksei Kazakov¹; Alexandra Galeeva¹; Aleksei Artamkin¹; Ludmila Ryabova¹; Sergey Dvoretsky²; Nikolay Mikhailov²; Mikhail Bannikov³; Sergey Danilov⁴; Sergey Ganichev^4
1M.V. Lomonosov Moscow State University, Russian Federation; ²A.V. Rzhanov Institute of Semiconductor Physics of SB RAS, Russian Federation; ³P.N. Lebedev Physical Institute of RAS, Russian Federation; ⁴University of Regensburg, Germany

We show that the terahertz photoconductivity in Hg1-xCdxTe-based films with the inverted band structure corresponding to the topological phase is asymmetric in magnetic field which may be considered as T-symmetry breaking. Beside that, the photoconductivity is asymmetric for two mirror-symmetric pairs of potential probes which may be treated as P-symmetry breaking. At the same time, the photoconductivity remains intact upon simultaneous swapping of both magnetic field and potential probe couple revealing thus the PT-symmetry.

14:45 Mo-PM1-4-3
Conductivity Measurement Of Graphene On Thin Polymeric Film By Broadband Air-plasma THz Spectroscopy
Binbin Zhou; Qian Shen; Patrick Whelan; Lujun Hong; Peter Jepsen
DTU Fotonik, Technical University of Denmark, Denmark

The sheet conductivity of graphene on thin polymer film can be accurately measured by air-plasma based ultra-broadband terahertz time-domain spectroscopy (THz-TDS). The transmitted THz echo signals are well separated in time due to the short THz pulse duration, and oscillation-free frequency dependent conductivity curves can be obtained.

15:00 Mo-PM1-4-4
Unveiling The Plasma Wave In The Channel Of Graphene Field-effect Transistor
Amin Soltani¹; Frederik Kuschewski²; Marlene Bonmann³; Andrey Generalov⁴; Andrei Vorobiev³; Florain Ludwig¹; Matthias M. Wiecha¹; Dovilė Čibiraitė¹; Frederik Walla¹; Susanne C. Kehr²; Lucas M. Eng²; Jan Stake³; Hartmut G. Roskos^1
1Goethe University Frankfurt, Germany; ²University of Technology, Dresden, Germany; ³Chalmers University of Technology, Sweden; ⁴Aalto University, Finland

Coupling an electromagnetic wave at GHz to THz frequencies into the channel of a graphene field-effect transistor (GFET) provokes collective charge carrier oscillations of the two-dimensional electron gas (2DEG) known as plasma waves. Here, we report the very first experimental and direct mapping of the electric field distribution in a gated GFET at nanometer length scales using scattering-type scanning near-field microscopy (s-SNOM) at 2 THz. Based on the experimental results we deduce the plasma wave velocity for different gate bias voltages, which is in good agreement with the theoretical prediction.

15:15 Mo-PM1-4-5
Excitation And Amplification Of The Unidirectionally Propagating Terahertz Plasmon In A Periodical Graphene Structure
Denis Fateev; Ilya Moiseenko; Konstantin Mashinsky; Viacheslav Popov
Kotelnikov Institute of Radio Engineerin and Electronics, Russian Academy of Science, Russian Federation

The amplification of the unidirectionally propagating plasmon modes excited by the incident terahertz wave in a periodical structure with an active graphene is studied theoretically. The amplification of propagating plasmon modes is due to radiative recombination in inverted graphene.

15:30 Mo-PM1-4-6
Experimental Investigation Of Graphene Layers As 2D Nanoelectrode For Continuous Wave Terahertz Generation
Alaa Jumaah; Shihab Al-Daffaie; Oktay Yilmazoglu; Franko Küppers; Thomas Kusserow
Technische Universität Darmstadt, Germany

The 2D photomixer investigation showed enhanced photocurrent for high THz output power. The number of graphene layers' effect directly the electrical and optical properties of the device. Higher transparency of a thinner graphene increased the illuminated effective area to increase the number of the generated carries. However, a thicker graphene is required to carry high current density and enhance the photomixer performance.

15:45 Mo-PM1-4-7
Modulation Behaviors, Conductivities, And Carrier Dynamics Of Single And Multilayer Graphenes
Emine Kaya¹; Nurbek Kakenov²; Coskun Kocabas²; Hakan Altan²; Okan Esenturk^2
1Middle East Technical Univeristy, Turkey; ²Bilkent University, Turkey

Time domain and time resolved terahertz studies of single- and multi-layer graphene (SLG and MLG) samples and modulator devices will be presented. A high performance up to 100% of modulators were observed with the devices even at very low voltages. High modulation depth over such a broad spectrum and simple device structure brings significant importance toward application of this type of device in THz and related technologies. In addition, conductivities of SLG and MLG devices were also investigated and a change in behavior was observed as the layer thickness increased. The charge carriers dynamics of the samples with pulp fluence and color was also highly interesting.

14:00-16:00 - Mo-PM1-5 - THz TDS 2 - Room 151

Chairperson: Mona Jarrahi

14:00 Mo-PM1-5-1

THz TDS System With 105 DB Dynamic Range Based On Transition Metal Doped InGaAs
Robert Kohlhaas¹; Steffen Breuer¹; Simon Nellen¹; Lars Liebermeister¹; Martin Schell¹; Mykhaylo Semtsiv²; William Masselink²; Björn Globisch^1
1Fraunhofer HHI, Germany; ²Humboldt University Berlin, Germany

A THz time-domain spectroscopy (TDS) system is presented, which uses photoconductive antennas made of iron and rhodium doped InGaAs. Due to the unique combination of ultrashort lifetime and high mobility as well as high resistivity, the transition metal doped InGaAs surpasses the performance of state-of-the-art photoconductors when applied as THz antennas: The presented THz TDS system features a spectral bandwidth of 6.5 THz and a dynamic range of up to 105 dB.

14:30 Mo-PM1-5-2
Comb-locked Frequency-domain Terahertz Spectrometer
Thomas Puppe; Yuriy Mayzlin; Julian Robinson-Tait; Rafal Wilk
TOPTICA Photonics AG, Germany

We introduce a frequency-domain spectrometers (FDS) based on a comb locked optical frequency synthesizer which combines scanning ranges of more than 3 THz at scan rates >300 GHz/s with frequency resolution in the order of 10 kHz. The comb provides a narrow linewidth spectrum which is absolutely referenced to a frequency standard (e.g. GPS). The inherent stability allows for favorable signal-to-noise scaling with measurement time.

14:45 Mo-PM1-5-3
Rapid Thickness Measurement With A SLAPCOPS-based Terahertz TDS System
Michael Kolano; Oliver Boidol; Daniel Molter; Georg von Freymann
Fraunhofer ITWM, Germany

Terahertz time-domain spectroscopy traditionally requires either one mode-locked laser and an external delay line or two mode-locked lasers with a controllable repetition rate difference. Here we demonstrate a polarization-multiplexed single-laser system, which combines the benefits of both approaches without any external delay line. The fiber laser emits two pulse trains with independently adjustable repetition rates, utilizing only one laser-active section and one pump diode. With a standard fiber-coupled terahertz setup, we are able to measure transients with a spectral bandwidth of 2.5 THz and a dynamic range of 50 dB in a measurement time of 1 s. An additional benefit of the underlying concept is the possibility for the rapid measurement of very thick samples usually not possible with traditional single-laser systems.

15:00 Mo-PM1-5-4
Deep Learning Approach For Removal Of Water Vapor Effects From THz-TDS Signals
Mikhail Mikerov; Jan Ornik; Martin Koch
Philipps-University Marburg, Germany

We propose a new very fast technique for the post-measurement removal of the water vapor effect on THz-TDS signals. Due to its very fast execution time and good generalization ability this technique has the potential to become an alternative to performing the measurements under dry atmosphere.

15:15 Mo-PM1-5-5
Terahertz Time-Domain Spectroscopy Up To 20 THz Based On Organic Electro-Optic Crystals
Mojca Jazbinsek¹; Tobias Bach²; Uros Puc¹; Vincent Michel¹; Carolina Medrano²; Peter Gunter^2
1Zurich University of Applied Sciences (ZHAW), Switzerland; ²Rainbow Photonics AG, Switzerland

We demonstrate ultrabroadband THz-wave generation and detection in a compact system based on a femtosecond fiber laser at 1560 nm and optical rectification in organic electro-optic crystals DSTMS. Terahertz time-domain spectroscopy with a spectrum extending up to 20 THz with a maximum bandwidth exceeding 70 dB is possible with this system.

15:30 Mo-PM1-5-6
Terahertz Time-domain Magneto-optic Spectroscopy Without The Polarization-resolution Technique
Masaya Nagai; Atsushi Nakane; Hiroyasu Suzukawa; Tomohide Morimoto; Masaaki Ashida
Osaka University, Japan

We propose a simple method for magneto-optic spectroscopy in the terahertz frequency regime without the conventional polarization-resolution technique. It is based on the time-domain reflection spectroscopy and employs circularly polarized terahertz light with magnetic field modulation. We experimentally demonstrate it for an InAs substrate. Our demonstration will help to advance multi-purpose characterization techniques for various semiconductors.

15:45 Mo-PM1-5-7
Characterization Of Thin Film Liquids By Multilayer Structure In THz Time Domain Reflection Spectroscopy
Qiushuo Sun¹; Xuequan Chen¹; Kai Liu¹; Xudong Liu²; Arturo Hernandez-Serrano³; Emma Pickwell-MacPherson^3
1the Chinese University of Hong Kong, Hong Kong; ²Shenzhen University, China; ³University of Warwick, United Kingdom

The characterization of thin film liquids is not as straightforward as bulk materials, as it requires accurate control of the thin film thickness and precise measurements of the amplitude and phase of the signals. We propose a multilayer structure for terahertz (THz) time domain reflection spectroscopy (TDRS) characterization of thin film liquids, the equations for this geometry are derived and the water-ethanol mixtures with various concentrations are measured, the refractive indices and absorption coefficients extracted from the proposed geometry and ordinary bulk reflection geometry match well. This work demonstrates that the proposed multilayer structure can be used to extract the optical properties of liquids by using a tiny amount of the sample, it can be potentially applied to characterize valuable biological aqueous solutions in the future.

14:00-16:00 - Mo-PM1-6 - QCL 2 - Room 101

Chairperson: Martin Wienold

14:00 Mo-PM1-6-1

Frequency Noise And Phase-locking Of A Quantum Cascade Laser-pumped, 1.073THz Molecular Laser Using A 1560nm Frequency Comb
Stefano Barbieri¹; Jean-Francois Lampin¹; Antoine Pagies¹; Giorgio Santarelli²; Hesler Jeffrey³; Wolfgang Hansel⁴; Ronald Holzwarth^4
1IEMN - CNRS Laboratory, France; ²Laboratoire LP2N - CNRS, France; ³Virginia Diodes Inc., United States; ⁴Menlo Systems GmbH, Germany

We report the measurement of the frequency noise power spectral density (PSD) of a THz molecular laser (ML) pumped by a mid-infrared (MIR) quantum cascade laser (QCL). This is obtained by beating the ML frequency with the harmonic of the repetition rate of a 1560nm frequency comb (FC). We find a frequency noise PSD < 10Hz2/Hz (-95dBc/Hz) at 100kHz from the carrier, limited by the noise of the QCL current driver. We also show that it is possible to actively phase-lock the QCL-pumped ML to the FC repetition rate harmonic by controlling the QCL drive current.

14:30 Mo-PM1-6-2
High-resolution Frequency And Phase Control Of A Terahertz Laser
Reshma A Mohandas¹; Alwyn Seeds²; Edmund Linfield¹; Giles Davies¹; Paul Dean¹; Lalitha Ponnampalam²; Joshua Freeman^1
1University of Leeds, School of Electronic and Electrical Engineering, United Kingdom; ²University College London, School of Electronic and Electrical Engineering, United Kingdom

We report on the high-resolution frequency and phase control of a terahertz (THz) quantum cascade laser (QCL). The 2.0 THz QCL is locked to a stable microwave reference frequency via an all-fibre infrared frequency comb. The frequency of the QCL is controlled by optical injection and the phase is independently controlled by introducing a phase-lock loop that provides electronic feedback to the QCL, forming an optical injection phase locked loop (OIPLL). By implementing this, for a fixed frequency, (1) the phase of the THz QCL relative to the microwave reference frequency can be controlled within a range 0.3Ãfââ?s¬, (2) the linewidth of the locked QCL was <1Hz (instrument limited) (3) the frequency and phase was stabilised for longer timescales.

14:45 Mo-PM1-6-3
Dispersion Measurements Of Terahertz Quantum Cascade Fabry-Perot Cavities And VECSELs
Tudor Olariu; Mattias Beck; Jerome Faist; Giacomo Scalari
ETH Zurich, Switzerland

A method for obtaining the dispersion of terahertz (THz) quantum cascade lasers (QCL) is presented. By measuring the relative phase of the center burst and first satellite peak within the interferogram of a sub-threshold THz QCL emitting cavity inside a Fourier Transform Infrared Spectrometer (FTIR), the electroluminescence spectrum is determined by Fourier Transform and the group velocity dispersion can be calculated. This method is applicable to any QCL -- here shown for Fabry-Perot (FP) ridge laser as well as VECSEL.

15:00 Mo-PM1-6-4
THz Quantum Cascade Lasers Operating Up To 210 K
Martin Franckie¹; Lorenzo Bosco¹; Mattias Beck¹; Elena Mavrona¹; Andreas Wacker²; Jerome Faist^1
1ETH Zürich, Switzerland; ²Lund Univsersity, Sweden

We present THz QCLs based on two quantum wells per period, designed and optimized with a nonequilibrium Green's function model, which lase up to 210 K cryostat temperature using a dry etched Cu-Cu double-metal waveguide

15:15 Mo-PM1-6-5
THz Quantum Cascade Laser Frequency Combs
Francesco Mezzapesa¹; Katia Garrasi¹; Valentino Pistore²; Lianhe Li³; A. Giles Davies³; Edmund Linfield³; Sukhdeep Dhillon²; Miriam Vitiello^1
1NEST, CNR - Istituto Nanoscienze and Scuola Normale Superiore, Italy; ²Laboratoire Pierre Aigrain, Departement de physique de l'ENS, France; ³School of Electronic and Electrical Engineering, University of Leeds, United Kingdom

We demonstrate THz optical frequency comb (FC) operation based on ultra-broadband, record dynamic range Quantum Cascade Lasers (QCLs) which exploit a heterogeneous active region design to achieve low and flat chromatic dispersion at the center of the gain curve. By implementing a Gires-Tournois Interferometer (GTI), as tightly coupled at one end of the QCL cavity, we provide lithographically-independent control of the free-running coherence properties of such THz-QCL FC and attain wide dispersion compensation regions, where stable and narrow (~3 kHz linewidth) single beatnotes extend over an operation range that is significantly larger than that of dispersion-dominated bare laser cavity counterparts.

15:30 Mo-PM1-6-6
Gain Dynamics In THz QCLs And Its Implication For THz Comb Sources
Christian Georg Derntl¹; Dominik Theiner¹; Giacomo Scalari²; Mattias Beck²; Jérôme Faist²; Karl Unterrainer¹; Juraj Darmo^1
1TU Wien, Photonics Institute, Austria; ²ETH Zürich, Institute of Quantum Electronics, ETH Zürich, Switzerland

In this contribution we present investigation of the interactions between the individual quantum cascade sections of a heterogeneous terahertz quantum cascade laser and their role in the stable operation of a broadband gain material. We employed THz-pump/THz-probe time domain spectroscopy (TDS) and reveal the spectrally resolved gain recovery time for each quantum cascade section that has multi-exponential decay character. Obtained results are discussed with respect to a frequency comb formation.

15:45 Mo-PM1-6-7
Self-Mixing Interferometry In Continuous-Wave High Power 1D And 2D QCL Random Lasers Operating At Terahertz Frequencies
Kimberly Reichel¹; Simone Biasco²; Teresa Crisci¹; Katia Garrasi¹; Francesco Mezzapesa¹; Miriam Vitiello^1
1NEST, CNR-Nano, Italy; ²NEST, Scuola Normale Superiore, Italy

We observe the first evidence of self-mixing in THz frequency quantum cascade random lasers fabricated in both wire and irregularly squared resonator architectures with surface photonic patterns. By reflecting the emitted light back into the laser cavity and changing the external cavity length, we observe the interference fringes within the laser cavity, thereby proving evidence of self-mixing. This paves the way to detectorless speckle-free imaging applications in the far-infrared.

15:45-16:15 - Coffee Break

16:30-18:15 Parallel sessions Mo-PM2

16:30-18:15 - Mo-PM2-1 - Gyrotron 3 - Amphi Lavoisier

Chairperson: Mikhail Glyavin

16:30 Mo-PM2-1-1
Development Of A Second Harmonic Multi-Frequency Gaussian Beam Output Gyrotron FU CW GVII
Yoshinori Tatematsu¹; Kyoya Takayama²; Yuto Maeda²; Tatsuya Ueyama²; Taisei Ogura²; Kazuki Nakagawa²; Ryota Kamiya²; Masafumi Fukunari²; Yuusuke Yamaguchi²; Teruo Saito^2
1FIR center, University of Fukui, Japan; ²University of Fukui, Japan

A sub-THz second harmonic multi-frequency gyrotron with Gaussian beam output, Gyrotron FU CW GVII, has been developed. This gyrotron was designed to change the frequency stepwise in the range from 270 to 420 GHz. Oscillations of seven second-harmonic modes were successfully observed and Gaussian beam radiations converted from six oscillation modes were observed. Two second harmonic modes; TE65 and TE85; oscillated in a single mode. Even in case of simultaneous oscillation of fundamental modes, radiation beams converted from second harmonic modes can be separated from the fundamental mode beams by making use of the different radiation directions emitted from the gyrotron window.

17:00 Mo-PM2-1-2
ECRH With 10 Gyrotrons At W7-X -- Achievements And Enhancements
Harald Braune; H.P. Laqua; K.J. Brunner; S. Marsen; D. Moseev; F. Noke; F. Purps; N. Schneider; T. Schulz; T. Stange; P. Uhren; F. Wilde; M. Zanini
Max-Planck-Institut für Plasmaphysik, Germany

Electron Cyclotron Resonance Heating (ECRH) was the main heating system during the operation campaign OP1.2b in 2018 of the W7-X stellarator [1]. The steady state capable ECRH system was used for plasma start-up, X-mode and O-mode heating as well as current drive (ECCD). The ECRH plant is equipped with 10 operational 140 GHz gyrotrons and a quasi-optical transmission line, which is operated under standard atmosphere conditions. The achieved plasma parameters with respect to the performance of the ECRH plant and prospective enhancements will be discussed

17:15 Mo-PM2-1-3
A 35GHz 100kW Klystron Amplifier Design
Fang Zhu
Institute of Electronics, Chinese academy of sciences, China

We present the design and modelling of a five-cavity, high-power klystron operating in Ka-band and paced with permanent magnet focusing system. The amplifier is powered by an electron gun operating at a voltage of 40 kV and a total current of 6 A. The circuit is comprised of four single-gap cavities and a three-gap extended interaction output cavity operating in the ?-mode. The main predicted characteristics of the klystron includes a 100 kW peak power at 35GHz, an efficiency of 40% and 42 dB gain.

17:30 Mo-PM2-1-4
Microwave-Band Chirped Pulse Amplification Technique Based On A System Of Helically Corrugated Waveguides
Irina Zotova; Naum Ginzburg; Lev Yurovskiy; Michael Vilkov; Alexander Sergeev; Sergey Samsonov; Alexander Bogdashov
Institute of Applied Physics RAS, Russian Federation

We consider the possible implementation of the Chirped Pulse Amplification (CPA) technique, widely used in optics, for the microwave frequency band. We propose using helically-corrugated waveguides for pulse stretching and compressing as their dispersion properties strongly depend on geometrical parameters. For stretched pulse amplification, a helical-waveguide gyro-TWT can be used as a broadband amplifier. Simulations with parameters of the experimentally realized 30 GHz gyro-TWT show that for a 300 W, 200 ps incident pulse, amplification up to 4 MW (40 dB) can be achieved in this system, while in the linear regime of the same gyro-TWT the output power is only about 250 kW.

17:45 Mo-PM2-1-5

Completion Of The 8 MW Multi-Frequency ECRH System at ASDEX Upgrade
Dietmar Wagner¹; Jörg Stober¹; Michael Kircher¹; Fritz Leuterer¹; Francesco Monaco¹; Max Münich¹; Martin Schubert¹; Hartmut Zohm¹¹; Gerd Gantenbein²; John Jelonnek²; Manfred Thumm²; Andreas Meier²; Theo Scherer²; Dirk Strauss²; Walter Kasparek³; Carsten Lechte³; Burkhard Plaum³; Alexander Zach³; Alexander Litvak⁴; Gregory Denisov⁴; Alexey Chirkov⁴; Vladimir Malygin⁴; Leonid Popov⁵; Vadim Nichiporenko⁵; Vadim Myasnikov⁵; Evgeny Tai⁵; Elena Solyanova^5
1Max-Planck-Institut für Plasmaphysik, Germany; ²Karlsruhe Institute of Technology, Germany; ³Universität Stuttgart, Germany; ⁴Insitute of Applied Physics, Russian Federation; ⁵Gycom Ltd, Russian Federation

Over the last 15 years, the Electron Cyclotron Resonance Heating (ECRH) system at the ASDEX Upgrade tokamak has been upgraded from a 2 MW, 2 s, 140 GHz system to an 8 MW, 10 s, dual frequency system (105/140 GHz). Eight gyrotrons were in routine operation during the current experimental campaign. All gyrotrons are step-tunable operating at 105 and 140 GHz with a maximum output power of about 1 MW and 10 s pulse length. The system includes 8 transmission lines, mainly consisting of oversized corrugated waveguides (I.D. = 87 mm) with overall lengths between 50 and 70 meters including quasi-optical sections at both ends. Further improvements of the transmission lines with respect to power handling and reliability are underway.

18:00 Mo-PM2-1-6
High-Gradient Test Results Of W-Band Accelerator Structures
Mohamed Othman¹; Julian Picard²; Samuel Schaub²; Valery Dolgashev¹; Sudheer Jawla²; Emma Snively¹; Bruno Spataro³; Richard Temkin²; Sami Tantawi¹; Emilio Nanni^1
1SLAC National Accelerator Laboratory, United States; ²Massachusetts Institute of Technology, United States; ³INFN-LNF, Italy

We report high-gradient test results for a 110 GHz single-cell standing wave accelerating cavity powered by a 1 MW gyrotron. The cavity is fed with 10 ns, 100s of kilowatt pulses, and achieved a field gradient up to 225 MV/m.

16:30-18:30 - Mo-PM2-2 - Solid State 3 - Petit Amphi

Chairperson: Manfred Helm

16:30 Mo-PM2-2-1
Terahertz Anomalous Hall Effect In Mn2-xPtSn
Di Liu¹; Artem Pronin¹; Anastasios Markou²; Claudia Felser²; Martin Dressel^1
1Universität Stuttgart, Germany; ²Max-Planck-Institute for Chemical Physics of Solids, Germany

Coherent-source THz spectroscopy was employed for measuring the Faraday rotation angle of Mn2-xPtSn films (x = 0; 0.2). In the THz experiments, we observe clear signatures of an anomalous Hall state, while any indications of the so-called topological Hall effect -- recently observed in these magnetically disordered systems in dc measurements - are absent. This demonstrates that the charge scattering mechanisms, responsible for the two phenomena, possess very different time scales: the anomalous Hall state is governed by the scattering process with the rates above THz frequencies, while the electron interaction, providing the topological Hall, possesses very low characteristic time scales.

17:00 Mo-PM2-2-2
Nonlinear Modulation Of Optical Absorption In Orthoferrites Due To Spin Precession Induced By Intense Terahertz Magnetic Field
Takayuki Kurihara¹; Motoaki Bamba²; Tohru Suemoto^3
1University of Konstanz, Germany; ²PRESTO, Japan Science and Technology Agency, Japan; ³Toyota Physical and Chemical Research Institute, Japan

We probe the transient change of near-infrared optical absorption in orthoferrites induced by coherent spin precession motion due to intense terahertz (THz) excitation. It has been found that under strong incident THz magnetic field strengths, the time profile of absorption exhibits periodic oscillation that is double the frequency of impulsively excited spin precession. The observed phenomena can be described by dielectric function which involves spin-spin exchange interaction. Our result demonstrates the potential of intense THz magnetic field in observing and controlling the fundamental interactions in magnetically ordered materials.

17:15 Mo-PM2-2-3
Ultrafast Terahertz Magnetometry
Wentao Zhang¹; Pablo Maldonado²; Zuanming Jin³; Keno Krewer¹; Jacek Arabski⁴; Guy Schmerber⁴; Eric Beaurepaire⁴; Tobias Kampfrath⁵; Mischa Bonn¹; Peter Oppeneer²; Dmitry Turchinovich^6
1Max Planck Institute for Polymer Research, Germany; ²Uppsala University, Sweden; ³Shanghai University, China; ⁴Institut de Physique et Chimie des Matériaux de Strasbourg, France; ⁵Freie Universität Berlin, Germany; ⁶Universität Bielefeld, Germany

THz emission spectroscopy is a powerful tool to access ultrafast magnetization dynamics in laser-excited magnetic systems. Here, we demonstrate femtosecond terahertz magnetometry, a method that can be used to rigorously reconstruct the (sub)picosecond-timescale magnetization dynamics in photoexcited ferromagnetic nanofilms from the magnetically-driven THz emission. Considering the propagation of the THz field from the surface of the film to the THz electro-optic sampling unit, we establish the transfer function, which allows us to obtain the ultrafast magnetization dynamics in the laser-excited sample in a calibrated manner.

17:30 Mo-PM2-2-4
Terahertz Pulsed-field Magneto-spectrometer At Room-temperature
Jean-Francois Lampin¹; Antoine Pagies¹; Stefano Barbieri¹; Ludovic Desplanque¹; Xavier Wallart¹; Jeffrey Hesler²; Oleksiy Drachenko³; Jean Leotin^3
1IEMN-CNRS, France; ²Virginia Diodes, United States; ³LNCMI, France

We have developed a compact pulsed-field THz magneto-spectrometer based on a THz molecular laser and heterodyne detection both at room-temperature. The recently developed continuous-wave THz laser uses mid-IR-pumped ammonia as active medium. The receiver is based on a subharmonic mixer pumped by a multiplication chain. A pulsed magnetic field up to 9 T is supplied by discharging a capacitor in a small coil at room-temperature. We demonstrate here the use of this spectrometer by measuring the effective mass of electrons in an InAs/AlGaSb heterostructure at room-temperature.

17:45 Mo-PM2-2-5
Magnon-polaritons In Dysprosium Ferrite
Marcin Bialek; Arnaud Magrez; Jean-Philippe Ansermet
Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland

We report on an experimental observation of a coupling of magnons with cavity photons at THz frequencies in an antiferromagnet dysprosium ferrite (DyFeO3). We show that magnon-polaritons can be observed and controlled in antiferromagnets. This brings the existing research on magnon-photon coupling to THz frequencies, because antiferromagnets have their magnetic resonances in this range even without external magnetic fields.

18:00 Mo-PM2-2-6
Magnetoelectric Excitations In Polar Antiferromagnetic Nickel Tellurates Substituted By Mn And Co
Christelle Kadlec¹; Stella Skiadopoulou¹; Maria Retuerto²; Filip Kadlec¹; Fedir Borodavka¹; Martin Misek¹; Martha Greenblatt²; Stanislav Kamba^1
1Institute of Physics CAS, Czech Republic; ²Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, United States

By a combination of infrared, Raman and time-domain THz spectroscopies, we studied spin and lattice excitations in Ni3TeO6 and its isostructural compounds obtained by substitution of Ni with Mn or Co. Low-temperature THz spectra revealed THz-range excitations sensitive to magnetic field; some of them can be assigned to electromagnons.

18:15 Mo-PM2-2-7
Ultrafast Magnetic Response In ε-Fe2O3 Nano Magnet Measured By Terahertz-pump Optical-Faraday-probe Measurement
MAKOTO NAKAJIMA¹; Hongsong Qiu¹; Shodai Kimoto¹; Kosaku Kato¹; Yohei Koike¹; Masashi Yoshimura¹; Kenta Imoto²; Marie Yoshikiyo²; Asuka Namai²; Seiji Miyashita²; Shin-ichi Ohkoshi^2
1Osaka University, Japan; ²the university of Tokyo, Japan

Ultrafast magnetic response in epsilon-iron oxide (ε-Fe2O3) nano magnet was measured by terahertz-pump optical Faraday probe measurement. Terahertz excitations induce the extremely fast response of the magnetization. The response time is within 400 fs which corresponds to the time duration of the terahertz pulses.

16:30-18:15 - Mo-PM2-3 - High Fields 1 - Room 269

Chairperson: Jozsef Fulop

16:30 Mo-PM2-3-1

Strong-field THz Nonlinearity On Gold Nanofilms

Tianshu Hong¹; Bing Song¹; Chen Ouyang³; Baolong Zhang³; Jungang Miao¹; Yutong Li²; Xiaojun Wu^{1 1}School of Electronic and Information Engineering, Beihang University, China; ²School of Physical Sciences, University of Chinese Academy of Sciences, China; ³School of Physical Sciences, University of Chinese Academy of Sciences, China

In summary, we show the nonlinearity of strong-field terahertz radiation on gold nanofilms, and propose that this phenomenon can be explained by the terahertz-induced electron delocalization in the gold nanostructures.

17:00 Mo-PM2-3-2
Terahertz-driven Acceleration Of A Relativistic 35 MeV Electron Beam
Morgan Hibberd¹; Alisa Healy²; Daniel Lake³; Vasileios Georgiadis¹; Elliott Smith⁴; Oliver Finlay³; Thomas Pacey⁵; James Jones⁵; Yuri Saveliev⁵; David Walsh⁵; Edward Snedden⁵; Robert Appleby⁴; Graeme Burt²; Darren Graham¹; Steven Jamison^3
1School of Physics and Astronomy & Photon Science Institute, The University of Manchester, United Kingdom; ²Department of Engineering, Lancaster University,United Kingdom; ³Department of Physics, Lancaster University, United Kingdom; ⁴School of Physics and Astronomy, The University of Manchester, United Kingdom; ⁵Accelerator Science and Technology Centre, Science and Technology Facilities Council, United Kingdom

We will present the first results from the CLARA research facility at Daresbury Laboratory demonstrating terahertz-driven acceleration of a relativistic 35 MeV electron beam. A polarization-tailored, frequency-tunable, narrowband terahertz source was used to directly excite the longitudinal accelerating mode of a dielectric-lined waveguide structure for collinear phase-velocity-matched THz-electron interaction.

17:15 Mo-PM2-3-3
Generation Of A Few Cycle Terahertz Pulse In Aperiodically Poled Lithium Niobate By Sequence Of Pump Pulses
Yuri Avetisyan¹; Ruben Miroyan¹; Apet Barsegyan²; Masayoshi Tonouchi^3
1Yerevan State University, Armenia; ²Integra Technologies, United States; ³Osaka University, Japan

It is shown that chirped aperiodically poled lithium niobate crystal is capable to generate powerful THz pulses with controllable number of THz field oscillations (from nearly single- to multi-cycles), when it is pumped by sequence of femtosecond laser pulses with chirped delays between adjacent pulses. The peak electric field strength of about 0.3 MV/cm (for non-focused THz beam) is predicted if intensity of each pump pulse in the sequence is 20 GW/cm2.

17:30 Mo-PM2-3-4
Frequency-and-polarization-controllable High-power THz Wave Generation Using Organic Nonlinear Optical Crystal
Isao Yoshimine; Masatsugu Yamashita; Hiromichi Hoshina; Mikiko Saito; Hiroaki Minamide; Chiko Otani
RIKEN Center for Advanced Photonics, Japan

Arbitrary control of high-power THz polarization and frequency is studied by the numerical calculation based on the coupled wave approach. THz wave generation using organic crystals via optical rectification provides high conversion efficiency. To avoid the limitation of the generated THz field direction which comes from their optical anisotropy, we propose the synthesis of THz wave generated from two crystals whose optical axis are orthogonal each other. By the calculation, the linearly and circularly polarized THz wave generation by changing the time delay of two pump pulses is demonstrated.

17:45 Mo-PM2-3-5
Exceptionally High THz Energy Densities Generated From Organic Crystals Pumped With Mid- Infrared Pulses
Claudia Gollner¹; Edgar Kaksis¹; Corinne Brodeur²; Valentina Shumakova¹; Andrius Baltuska¹; Audrius Pugzlys¹; Mostafa Shalaby^2
1Photonics Institute, TU Wien, Austria; ²Swiss Terahertz Research-Zurich, Switzerland

We investigate THz generation in organic crystals (DAST and DSTMS) by optical rectification of intense Mid-Infrared pulses. The broadband spectrum exceeds several octaves when pumped by 100 fs, 3.9 μm pulses. We report on an extraordinarily high THz energy density and crystal damage threshold > 120 mJ/cm2.

18:00 Mo-PM2-3-6
Towards MJ-level Ultrashort Terahertz Generated By Optical Rectification With A Compact Terawatt Laser
Antoine Courjaud; Jean-Gabriel Brisset; Pierre Sevillano; Emilien Gontier
Amplitude Systemes, France

We report on the development of a compact diode-pumped Terawatt laser for generation of intense Terahertz pulses by optical rectification in LiNbO3. Using a 15mJ compact ultrafast laser already allowed to demonstrate 150µJ Terahertz, with 0,36% conversion efficiency. We report on a laser delivering 250mJ at 50Hz repetition rate and 480fs pulse duration, holding the potential to generate 1mJ-level Terahertz ultrashort in an equivalent setup.

16:30-18:15 - Mo-PM2-4 - 2D Materials 2 - Room 162

Chairperson: Renbin Zhong

16:30 Mo-PM2-4-1

Cavity-mediated Bound Excitons
Erika Cortese¹; Linh Ngoc Tran²; Jean-Michel Manceau³; Giorgio Biasiol⁴; Iacopo Carusotto⁵; Raffaele Colombelli⁶; Simone De Liberato^1
1University of Southampton, Department of Physics and Astronomy,United Kingdom; ²Universite Paris-Sud, Centre de Nanosciences et de Nanotechnologies, C2N-Orsay, France; ³Univ. Paris-Sud, Centre de Nanosciences et de Nanotechnologies, CNRS UMR 9001,C2N-Orsay, France; ⁴Laboratorio TASC, CNR-IOM, Italy; ⁵Universita di Trento, INO-CNR BEC Center and Dipartimento di Fisica, Italy; ⁶Univ. Paris-Sud, Centre de Nanosciences et de Nanotechnologies,CNR, C2N-Orsay, France

We experimentally demonstrate the existence of bound excitonic resonances in doped quantum wells whose electron and hole are bind by the exchange of virtual cavity photons. The theory predicts that above a certain coupling threshold a novel discrete resonance appears below the ionisation edge. In our case, the ionisation edge corresponds to the onset of the continuum above the QW barriers. This resonance describes a polaritonic excitation: part-photon and part-bound exciton. Using a sample consisting of 13 GaAs/AlGaAs n+-doped semiconductor QWs embedded in a metal / active region / metal grating cavity, we were then able to experimentally observe such a discrete resonance. We thus provided a first demonstration of the existence of a bound state of two charged particles kept together not by Coulomb interaction but by the exchange of virtual cavity photons.

17:00 Mo-PM2-4-2
The Upper Branch Broadening In Ultrastrongly Coupled THz Landau Polaritons
Shima Rajabali; Giacomo Scalari; Janine Keller; Mattias Beck; Jerome Faist
ETH Zurich, Switzerland

We present our investigation on ultrastrong coupling of the Landau level transitions in a two dimensional electron gas to complementary split ring resonator arrays, as a terahertz metasurface. To achieve a higher coupling rate, the capacitive gap of the resonator is reduced systematically. This increment in the coupling rate is expected due to the enhanced vacuum field fluctuations in a smaller volume mode. However, our results indicate that the gap size reduction introduces a broadening in the upper polariton branch below a certain gap width.

17:15 Mo-PM2-4-3
A New Tunable Topological Platform With Terahertz Band Gap: Pb1-xSnxSe
Gauthier Krizman¹; Badih Assaf²; Günther Bauer³; Gunther Springholz³; Robson Ferreira¹; Gérald Bastard¹; Louis-Anne de Vaulchier¹; Yves Guldner^1
1Ecole Normale Supérieure, France; ²University of Notre Dame, United States; ³Johannes Kepler Universität, Austria

In topological insulator thin films, new states of matter can be generated by hybridizing the massless Dirac states that occur at the topological insulator surface. In this work, we experimentally introduce a platform where this hybridization can be continuously tuned: the PbSnSe topological superlattice. Using magnetooptical transmission spectroscopy on high quality molecular beam epitaxy grown PbSnSe/ PbEuSe superlattices, we demonstrate that the energy gap emerging from this hybridization can be tuned with temperature from 1 to 10 THz. The engineering of topological states is a promising road to achieve photodetection and/or photoemission in the terahertz range.

17:30 Mo-PM2-4-4
Control Of Terahertz Nonlinearity In Graphene By Gating
Hassan A. Hafez Eid¹; Klaas-Jan Tielrooij²; Mischa Bonn³; Dmitry Turchinovich^1
1University of Bielefeld, Fakultät für Physik, Germany; ²Catalan Institute of Nanoscience and Nanotechnology, Spain; ³Max Planck Institute for Polymer Research, Germany

We study the dependence of the terahertz (THz) nonlinearity of graphene and its temporal dynamics on the free carrier concentration by THz-pump/THz-probe spectroscopy of a gated graphene at room temperature. The strong THz nonlinearity is attributed to electron heating by the driving THz field and shows a drastic dependence on the background electron concentration, demonstrating a wide-range tunability of the THz nonlinearity of graphene.

17:45 Mo-PM2-4-5
Nonlocal Photoresponse In Epitaxial Hg1-xCdxTe Films With The Inverted Band Structure
Aleksei Kazakov¹; Alexandra Galeeva¹; Alexey Artamkin¹; Sergey Dvoretskiy²; Nikolay Mikhailov²; Mikhail Bannikov³; Sergey Danilov⁴; Liudmila Ryabova⁵; Dmitry Khokhlov^1
1M.V. Lomonosov Moscow State Univ., Faculty of Physics, Russian Federation; ²Rzhanov Institute of Semiconductor Physics, Russian Federation; ³P.N. Lebedev Physical Institute, Russian Federation; ⁴Regensburg University, Germany; ⁵M.V. Lomonosov Moscow State University, Faculty of Chemistry, Russian Federation
We present our results on terahertz photoconductivity studied in Hg1-xCdxTe epitaxial films with the inverted energy spectrum (x<~0.16) in the nonlocal (H-bar type) geometry. We show that the terahertz photoresponse demonstrates nonlocality and asymmetry in magnetic field. We discuss the results in terms of a qualitative model that takes into account coexistence of the bulk transport and boundary conductive channels.

18:00 Mo-PM2-4-6
Hot Carrier Recombination Close To The Dirac Point In Graphene-hBN Van Der Waals Heterostructures
Panhui Huang; Elisa Riccardi; Federico Valmorra; Jérôme Tignon; Sukhdeep Dhillon; Bernard Plaçais; Robson Ferreira; Juliette Mangeney
Ecole Normale superieure, France

We investigate the photoconductive regime in graphene-hBN heterostructures close to the Dirac point. We demonstrate recombination lifetimes of non-equilibrium carriers in excess of 30 ps under continuous mid-infrared illumination (i.e. with photon energy below optical phonon energy in graphene). We also demonstrate the onset of an effective recombination channel relying on electron-hyperbolic phonon coupling by increasing bias. This study opens interesting perspectives to exploit graphene-hBN van der Waals heterostructures with long carrier lifetimes for THz lasing and highly sensitive THz photodetection. Our work also paves the way to develop graphene-based sources for phonon polariton optics.

16:30-18:15 - Mo-PM2-5 - Material 1 - Room 151

Chairperson: Adrien Dobroiu

16:30 Mo-PM2-5-1
Optoelectronic Properties Of Tin-Based Hybrid Metal Halide Perovskite Thin Films For Photovoltaics
Rebecca Milot¹; Michael Johnston²; Laura Herz^2
1The University of Warwick, Department of Physics, United Kingdom; ²University of Oxford, Clarendon Laboratory, UK
Due to their exceptional optoelectronic properties, hybrid metal halide perovskites thin films have shown extraordinary success as active layers in solar cells. One potential drawback of hybrid perovskites, however, is that the highest performing devices are currently based around toxic, lead-containing materials. Although tin is a promising replacement for lead, p-doping in tin-based materials has prevented them from achieving the efficiencies of their lead-based analogues. Using optical-pump/THz-probe spectroscopy and THz time-domain spectroscopy, we compare the intrinsic and extrinsic optoelectronic properties formamidinium tin triiodide thin films and comment on the fundamental limits to charge transport.

17:00 Mo-PM2-5 -2
Improved Terahertz Effective Media Models For Mixtures Of Polar Liquids
Juin W. Zhou; M. Hassan Arbab
State University of New York at Stony Brook, United States

We present two improved mixed media models for solutions of polar liquids in the THz regime. Simple effective media models do not consider intermolecular interactions or hydrogen bond network distributions in polar liquid solutions, and therefore yield inaccurate estimates of the effective dielectric functions. We present two new models: a volumetric modification to the Bruggeman equation and an effective time constant calculation in Debye-like relaxations. Furthermore, we will discuss the limitations of each model in predicting the dielectric functions.

17:15 Mo-PM2-5 -3
Investigation Of Laser-Patterned Silicon Transmittance In The Frequency Range Of 0.1-4.7 THz
Evaldas Svirplys¹; Simonas Indrisiūnas²; Heiko Richter³; Andrzej Urbanowicz⁴; Linas Minkevicius¹; Till Hagelschuer³; Gediminas Raciukaitis²; Heinz-Wilhelm Hubers³; Irmantas Kasalynas^1
1Center for Physical Sciences and Technology, Terahertz Photonics Laboratory, Lithuania; ²Center for Physical Sciences and Technology, Laser Microfabrication Laboratory, Lithuania; ³German Aerospace Center, Institute of Optical Sensor Systems, Germany; ⁴Center for Physical Sciences and Technology, Laboratory of Ultrafast Optoelectronics, Lithuania
The dependence of THz transmittance on the surface roughness of differently laser-patterned silicon was investigated in the frequency range of 0.1-4.7 THz. The scattering of THz waves on rough silicon surface was found as the main mechanism that determines optical losses. The impact of silicon processing in ambient air and argon-rich environments on the THz absorption losses was also observed.

17:30 Mo-PM2-5 -4
Retrieving Permittivity Model Parameters For Polar Liquids And Multilayer Systems Through THz-TDS Time-trace Data Analysis
Melanie Lavancier; Sergey Mitryukovskiy; Nabil Vindas; Jean-François Lampin; Romain Peretti
IEMN, CNRS UMR 8520, France

We present new features of the Fit@TDS software for the analysis of polar liquids and multilayer systems. We also show that the modeling of the absorption coefficient of polar liquids can be improved above 2.5THz. Hence, this software will enable us to retrieve the parameters of the models depicting polar liquids. It will help to analyze and compare charges motions, playing an important role in biology and chemistry with such effects as protein solvation. Finally, the implementation of a scattering model will improve the accuracy of the results. These features will be illustrated with THz-TDS experiments on biological samples (sugars, amino acids, enzymes, emulsions).

17:45 Mo-PM2-5 -5
Observation Of Phase Change Of Methane Hydrate Using THz Waves
Keisuke Matsumura; Kei Takeya; Kodo Kawase
Nagoya University, Japan

We observe a phase change of methane hydrate, which is expected to be a new energy resource, using THz Time-Domain Spectroscopy (THz-TDS). In the temperature zone where methane hydrate should be decomposed, an increase in absorption and a shift in time-domain waveform are observed, which seems to indicate that the sample is mutated.

18:00 Mo-PM2-5 -6
Redox Chemistry In Eumelanin
Zarina Gagkaeva¹; Konstantin Motovilov²; Vadim Grinenko³; Maxim Savinov⁴; Lenar Kadyrov²; Alexei Pronin⁵; Zakhar Bedran²; Elena Zhukova²; Bernard Mostert⁶; Boris Gorshunov^2
1Moscow Institute of Physics and Technology, Russian Federation; ²MIPT, Russian Federation; ³Institute for Solid State and Materials Physics, Germany; ⁴Institute of Physics of the Czech Academy of Sciences, Czech Republic; ⁵Prokhorov General Physics Institute of the Russian Academy of Sciences, Russian Federation; ⁶Department of Chemistry, Swansea University, United Kingdom

Eumelanin is a perspective conductive biomolecular material, which has already been used for making various bioelectronic devices ranging from transistors to batteries. It is known that its conductivity mechanisms are governed by a redox comproportionation reaction. However, most studies devoted to the redox chemistry of eumelanin lack the data on the temperature behavior of its properties. We use broadband dielectric spectroscopy and heat capacity measurements to study the influence of hydration and temperature on eumelanin's conductivity.

16:30-18:15 - Mo-PM2-6 - Instrum. Biology - Room 101

Chairperson: Gun-Sik Park

16:30 Mo-PM2-6-1
An Ultrasensitive Terahertz Microfluidic Chip Based On Fano Resonance Of A Few Arrays Of Meta-atoms
Kazunori Serita; Hironaru Murakami; Iwao Kawayama; Masayoshi Tonouchi
Osaka University, Japan

We present a nonlinear optical crystal-based terahertz (THz)-microfluidic chip with a few arrays of asymmetric meta-atoms for the measurements of trace amount of solutions. A near-field THz emission source that is locally generated in the process of optical rectification at the irradiation spots of fs laser beams induces a high-Q Fano resonance and modifies the resonance frequency of the meta-atoms when the channel between meta-atoms is filled with solutions with different concentrations. Using this chip, we successfully detected attomole order of solute in a less than 100 pL volume of the solution.

17:00 Mo-PM2-6-2
An Optical Instrument For The Submillimeter Spectroscopy Of The Volatile Metabolome
François Bondu¹; Goulc'hen Loas¹; Ludovic Frein¹; Cyril Hamel¹; Anthony Carré¹; Virginie Daburon²; Françoise Binet²; Guillaume Ducournau³; Jean-François Lampin^3
1CNRS, Univ Rennes, Institut FOTON UMR6082, France; ²CNRS, Univ Rennes, ECOBIO UMR 6553, France; ³CNRS, Université Lille 1, IEMN UMR 8520, France

We are designing and realizing an instrument for the spectroscopy of the volatile metabolome of the soil microorganisms. The use of optical telecommunication elements makes it possible to realize a compact source with a wide range of accessible frequencies (100 GHz - 1 THz range; 3-33 cm?¹) with an accuracy of 10? Hz (3.10?? cm?¹), as well as a low bandwidth detection system. The instrument will discriminate among complex polar molecules. We report on the preliminary performances of parts of the source system.

17:15 Mo-PM2-6-3
Towards Broadband THz Spectroscopy And Analysis Of Sub-wavelength-size Biological Samples
Sergey Mitryukovskiy; Mélanie Lavancier; Flavie Braud; Yue Bai; Emmanuel Dubois; Jean-François Lampin; Romain Peretti
IEMN CNRS/Université de Lille, France

We report on our recent progress toward bio-photonic applications of terahertz time-domain spectroscopy. First, we developed a technique for the confinement of broadband terahertz pulses to a sub-wavelength-volume, and will present its applications to study biological samples. Second, we will discuss the analysis of terahertz time-trace data from bio-samples using our Fit@TDS software based on the time-domain optimization algorithm that enables direct fitting of sample parameters. The combination of these (the experimental and the modelling) techniques is a robust tool for terahertz bio-photonics.

17:30 Mo-PM2-6-4
Technique For Recording THz Response From Bio-Tissue
Maksim Fomin¹; Konstantin Taranets¹; Nikolay Bagraev²; Leonid Klyachkin²; Vladislav Odintsov³; Vyacheslav Bazarbaev^4
1Peter the Great St.Petersburg Polytechnic University (SPbPU), Russian Federation; ²Ioffe Institute, Russian Federation; ³St Petersburg Clinical hospital of RAS, Russian Federation; ⁴ANO CPE "Institute of Mammology", Russian Federation

The results obtained show the promise of further research in the field of recording THz response from biological tissue with the SNS balance device.

17:45 Mo-PM2-6-5
Quantification Of DsDNA Functionalization Efficiency In THz Biosensors
Christian Weisenstein¹; Merle Schmeck¹; Dominik Schaar²; Anna Katharina Wigger¹; Anja Bosserhoff²; Peter Haring Bolívar^1
1University of Siegen - High Frequency and Quantum Electronics, Germany; ²Friedrich-Alexander-University Erlangen-Nürnberg, Germany

In the past, THz bioanalytical techniques have been proven to be viable tools for label-free detection of biomolecules. However, significant improvements in the detection limit are needed to apply THz biosensors in biomedical diagnosis. To determine detection limits of the biosensor and the absolute amount of sample volume, quantitative measurements are required. We present label-free THz sensing of dsDNA and implement an approach based on reference investigations to quantify the dsDNA functionalization density. Defined functionalization densities are vital to maximize the adsorption of a dsDNA groove-binding protein, which acts as a tumor marker for malignant melanoma.

18:00 Mo-PM2-6-6
Pressure Controlled In Vivo THz Measurements Of Skin: Monitoring The Effects Of Moisturizers
Hannah Lindley¹; A. I. Hernandez-Serrano¹; Qiushuo Sun²; Jiarui Wang²; Emma Pickwell-MacPherson^1
1University of Warwick, Dpt of Physics, United Kingdom; ²Chinese University of Hong Kong, Dpt of Electronic Engineering, Hong Kong

Pressure is a variable which must be controlled during in vivo skin measurements if comparisons between subjects and measurements are to be obtained. We have built a device to indicate (and record) if the contact pressure between the skin and the imaging window is within the desired range at the time of measurement. Using this device, terahertz (THz) measurements of skin before and after the application of a commercial skin-care product were taken. Significant changes in the THz skin properties were observed, which cannot therefore be attributed to varying contact pressure. These results demonstrate that with a rigorous protocol THz imaging has the potential to be used for testing new skin products and quantifying their effects on the skin and how long these last.

18:15-19:30 - Poster session - Mo-Po 1 - Room 8

Mo-Po1-1
Scattering Of THz Radiation By Spherical MWCNTs Aerogel In State Of Acoustic Levitation
Alexander Badin¹; Igor Dorofeev¹; Grigorii Dunaevskii¹; Valentin Suslyaev¹; Dmitriy Bodazhkov¹; Kseniya Simonova¹; Sergey Moseenkov²; Vladimir Kuznetsov^2
1National Research Tomsk State University, Russian Federation; ²Boreskov Institute of Catalysis SB RAS, Russian Federation

Recently created aerogel with multi-walled carbon nanotubes (MWCNTs) finds more and more new applications due to its unique properties: optimal weight and dimensional parameters, strength, and electrical conductivity. One of MWCNTs aerogel application may be used as a probe fixed in an acoustic standing wave in a tract of a terahertz spectrometer. Therefore, it is of interest to carry out research of the THz radiation scattering by aerogel. The transmission coefficient measurements at various positions of the aerogel in the beam using a BWO spectrometer at the frequency range 63-124 GHz were made. For levitation of aerogel we use acoustic levitation cell based on local transducers. Average diameter of MWCNTs aerogel was 2.7 mm. The calculation of extinction of ideal conductive balls with a diameter of 2.75 mm (MWCNTs aerogel with a specific conductivity of 103 Sm/m and ideally conductive) was carried out.

Mo-Po1-2
FT-ESR Measurements On BDPA By Pulsed ESR Using A Gyrotron As High-power Millimeter Wave Source
Seitaro Mitsudo; Kaishi Kono; Kazuki Dono; Kanata Hayashi; Yuya Ishikawa; Yutaka Fujii
Research Center for Development of Far-Infrared Region, University of Fukui, Japan

Pulsed ESR spectroscopy system was developed using the high-power millimeter wave of gyrotron. The FID signal of stable radicals of BDPA diluted with polystyrene was successfully observed by the quadrature detection method. By Fourier transforming of these FID signals, high resolution FT-ESR spectrum of BDPA was successfully obtained.

Mo-Po1-3
The Fundamental Terahertz Mode Of L-Alanine: Strong Narrowing, Greater Symmetry And Small And Non-Uniform Shift As Temperature Is Reduced
Thomas Sanders; Jackson Allen; Matthew Large; Josip Horvat; Roger Lewis
University of Wollonogong, Australia

We have measured the spectrum of L-alanine in the terahertz region over a wide temperature range, from 15 to 300 K. At the lowest temperature, the fundamental line is very sharp, of intrinsic width 0.02 THz (0.8 cm-1). As temperature increases, the line broadens, undergoes a non-uniform red shift, becomes more asymmetrical and decreases in oscillator strength.

Mo-Po1-4
Density Of State Of Low-frequency Intramolecular Vibrations For Stiff And Flexible Molecules At Solid Phase
Feng Zhang¹; Hong-Wei Wang²; Keisuke Tominaga¹; Michitoshi Hayashi²; Tetsuo Sasaki^3
1Molecular Photoscience Research Center, Kobe University, Japan; ²Center for Condensed Matter Sciences, National Taiwan University, Taiwan; ³Research Institute of Electronics, Shizuoka University, Japan

Densities of state (DOS) of intramolecular vibrations in optical phonon modes have been quantitatively studied for three oligoglycines. Polycyclic aromatic chain molecules have been used as references. We found that the more flexible backbones of oligoglycines lead to drastically faster growth of intramolecular vibrations with the increase of frequency than the stiffer backbones of polycyclic aromatics do.

Mo-Po1-5
Ionic Current In Superionic Conductor Na+ Beta-Alumina Induced By Terahertz Electric Fields
Yasuo Minami¹; Benjamin Ofori-Okai²; Prasahnt Sivarajah³; Ikufumi Katayama⁴; Jun Takeda⁴; Keith Nelson³; Tohru Suemoto^5
1Tokushima University, Japan; ²SLAC National Accelerator Laboratory, United States; ³Massachusetts Institute of Technology, United States; ⁴Yokohama National University, Japan; ⁵Toyota Physical and Chemical Research Institute, Japan

We demonstrate that intense terahertz (THz) electric-field transients can manipulate the motion of ions in an ionic conductor. The cations trapped in local potential minima are accelerated by single-cycle THz pulses leading to a macroscopic current flow.

Mo-Po1-6
Response Of Strongly Nonequilibrium Plasma Created By High Power Short UV Laser Pulse In Rare Gases To THz Frequency Band Emission
Alexander Popov; Anna Bogatskaya; Ekaterina Volkova
Moscow State University, Russian Federation

The response of plasma created by multiphoton gas ionization in an intense UV laser pulse to the terahertz frequency band radiation is studied. Analysis is based on the Boltzmann equation for the temporal behavior of the electron velocity distribution function (EVDF) in an arbitrary external electric field and allows to take into account both temporal retardation of the EVDF evolution with respect to the external electric field and the effect of the relaxation of the strongly nonequilibrium EVDF due to elastic electron - atomic collisions. The suggested theory enables to properly describe propagation of ultra-short THz pulses in laser plasma waveguides.

Mo-Po1-7
Dynamics Of A Sub-terahertz Discharge In The Heavy Noble Gases Produced By A High-density Radiation Field
Alexander Sidorov; Sergey Razin; Alexey Veselov; Mikhail Victorov; Alexander Vodopyanov; Mikhail Morozkin; Mikhail Proyavin; Mikhail Glyavin
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

Results of the experimental investigation of the discharge front propagation in the beams of powerful sub-terahertz radiation are presented. The front propagation velocity is measured in the wide range of the gas (argon, krypton) pressure (0.1 -- 1 atm). It is demonstrated that the discharge front runs against the incident sub-terahertz radiation beam into the region with the electric field value well below the threshold. Discharge propagation slowing down in correspondence with the electric field strength decrease. Characteristic propagation velocity value is in the range of 10^5 -- 10^6 cm/s.

Mo-Po1-8
A Coherent Smith-Purcell Radiation Source: Design Considerations For A High Power, Tunable Source Of Terahertz Radiation
Huibo Zhang; Ivan Konoplev; George Doucas
John Adams Institute for Accelerator Science, Department of Physics, University of Oxford, United Kingdom

The concept of coherent terahertz (THz) tunable Smith-Purcell radiation source driven by the microbunched electron beam is presented. Studies were performed using numerical and analytical approaches to investigate the radiation generated by electron microbunches. It is demonstrated that the capability of manipulating the microbunching of electron beams results in the possibility to control both the radiation power and the frequency of coherent Smith-Purcell radiation (cSPr). Numerical results were compared with analytical calculations and there is a good agreement between them. These proof of concept studies demonstrate the possibility of designing a high power, broadly tunable THz radiation source.

Mo-Po1-9
Modulation Of Terahertz Wave Based On A Preionized Plasma
Liangliang Zhang¹; Tong Wu²; Hang Zhao²; Rui Zhang³; Cunlin Zhang¹; Yuejin Zhao^2
1Capital Normal University, Department of Physics, China; ²Beijing Institute of Technology, China; ³Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, China

We demonstrate the modulation of terahertz wave generation from two-color femtosecond laser filament on the basis of a preionized air plasma background created by a modulation pulse using an orthogonal pumping geometry. This is achieved by adjusting and optimizing the phase difference between the two-color laser fields, which is introduced when the two-color fields goes through the preionized air plasma. The results are reasonably coincident with our theoretical simulation based on the plasma photocurrent model. Our results can contribute to the further understanding of the generation mechanism of terahertz wave, enhance the generation efficiency and expand the practical application of terahertz wave.

Mo-Po1-10
3-D Calculations Of Terahertz Generation In The Tilted-pulse-front Scheme
Lu Wang; Franz kaertner
DESY, Germany

The tilted-pulse-front setup utilizing a diffraction grating is one of the most successful methods to generate single- to few-cycle terahertz pulses. However, the generated terahertz pulses have a large spatial inhomogeneity, due to the noncollinear phase matching condition and the asymmetry of the prism-shaped nonlinear crystal geometry, especially when pushing for high optical-to-terahertz conversion efficiency. Thus, a 3D+1 numerical model is necessary for investigating the terahertz generation problem in the tilted-pulse-front scheme. In this article, we compare the differences of the 1D+1, 2D+1 and 3D+1 numerical models. The simulation results suggest a strong spatial dependence on the generated terahertz electric field. The single-cycle pulses are only generated at the neighborhood around the apex of the prism. This strong spatial dependence must be accounted for when using the terahertz pulses for strong-field physics and carrier-envelope-phase sensitive experiments

Mo-Po1-11
High Cubic Nonlinearity Of Liquids In The Broadband THz Spectral Range
Maria Zhukova¹; Maksim Melnik¹; Anton Tcypkin¹; Irina Vorontsova¹; Sergey Putilin¹; Sergei Kozlov¹; Xi-Cheng Zhang^2
1ITMO University, Russian Federation; ²University of Rochester, United States

Here we report the direct measurement of the nonlinear refractive index coefficient of liquids by using the Z-scan method with broadband pulsed THz beam. The results fit with conventional Z-scan analytics well. We estimate the nonlinear refractive index coefficient n2 of liquids through the use of the theoretical treatment that takes the ionic vibrational contribution into account. This estimation correlates with experimental data obtained.

Mo-Po1-12
Intersubband Terahertz Emission From Coupled GaAs/AlGaAs Double Quantum Wells Under Interband Photoexcitation
Alexander Andrianov; Alexey Zakhar'in
Ioffe Institute, Russian Federation

Terahertz range photoluminescence from specially designed structures with tunnel coupled double quantum wells under interband optical excitation has been investigated. A series of narrow emission lines were observed and interpreted as intersubband radiative transitions between electron quantum confinement levels.

Mo-Po1-13
Transformation Of The Terahertz Polarization During Three-Wave Joint Propagation In Liquid Nitrogen
Petr Solyankin¹; Alexander Shkurinov²; Nikolai Kuzechkin¹; Alexei Balakin²; Vladimir Makarov^2
1ILIT RAS - Branch of the FSRC «Crystallography and Photonics» RAS, Russian Federation; ²Lomonosov Moscow State University, Russian Federation

In this work we experimentally and theoretically investigate the mutual action of three copropagating waves in isotropic nonlinear medium (liquid nitrogen). Two waves are the first and the second harmonic of the Ti:Sa laser system, and the third one is the terahertz wave generated in the spark of optical breakdown of air. After propagation through liquid nitrogen the change in terahertz polarization state is observed. We attribute this phenomenon to the nonlinear "Terhune-like" mutual rotation of the main axis of a polarization ellipse of terahertz radiation.

Mo-Po1-14
Optimization Of Terahertz Source Via An Ambient Air-Based Multi-Color Photoionization
Po-Hsun Wu¹; Chan-Shan Yang²; Po-Hsun Chen³; Wei-Che Hu³; Hai-Wei Du⁴; Xiao-Yu Peng⁵; Ci-Ling Pan^1
1National Tsing Hua University, Taiwan; ²Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taiwan; ³National Tsing Hua University, Taiwan; ⁴Nanchang Hangkong University, China; ⁵Center for Terahertz Technology Research, Chongqing Institute of Green and Intelligent Technology, China

By applying the well-known transient current model, theoretically investigating terahertz (THz) emission from gas plasma induced by multi-color femtosecond laser pulses has been developed in this work. Instead of static tunneling ionization model, we adopted Ammosov-Delone-Krainov (ADK) tunneling ionization model to calculate the tunneling ionization rate. In three-color pumping schemes, the optimal power ratio tends to require a larger amount of fundamental field with the increment of total pump power. The optimal relative phases for the 2nd harmonic and 3rd harmonic field are 0.5πand π , respectively.

Mo-Po1-15
On The Prospects For The Study Of A Point Discharge Sustained By A Terahertz Free Electron Laser Radiation In An Inhomogeneous Gas Flow
Alexander Vodopyanov¹; Alexander Sidorov¹; Alexey Veselov¹; Vitaly Kubarev²; Oleg Shevchenko²; Yaroslav Gorbachev^2
1Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation; ²Budker Institute of Nuclear Physics RAS, Russian Federation

It is proposed to use high-power radiation from a terahertz free electron laser to create a localized (point-like) discharge in an inhomogeneous gas flow. Plasma parameters that can be achieved in such a system open up prospects for creating an effective point-like source of extreme ultraviolet light for the next-generation projection lithography.

Mo-Po1-16
High Conversion Efficiency In The System "Nonlinear-Optical Crystal Partially Filling The Cross Section Of A Rectangular Waveguide"
Anahit Nikoghosyan
Yerevan State University, Armenia

It is shown that terahertz radiation (0.1-3 THz) can be effectively generated via optical rectification of femtosecond laser pulses in a system of a "nonlinear-optical crystal partially filling the cross section of a rectangular metal waveguide". The numerical calculations for the phase-matching in LiNbO3, ZnTe, DAST and GaSe nonlinear optical crystals have been performed. The influence of THz radiation absorption on the efficiency of generation of coherent THz radiation in the system has been investigated.

Mo-Po1-17
Strong Terahertz Electromagnetic Wave Generation Due To Intense Laserplasma Interaction Mechanisms
Andrey Kuratov¹; Andrey Brantov²; Yuriy Aliev²; Valery Bychenkov^2
1Center of Fundamental and Applied Research, VNIIA, Russian Federation; ²Lebedev Physical Institute RAS, Russian Federation

Strong THz waves have a wide range of applications. Laser -- plasma interaction has advantages over other methods for high power THz generation. We report on our theoretical and numerical investigations of three different mechanisms of THz radiation generation from the laser-plasma sources. We have identified the most effective mechanism of THz pulse generation and quantitatively characterized its properties.

Mo-Po1-18
Terahertz Wave Generation Using Single Or Few-Cycle Laser Pulses In A Gaseous Medium
Rajaram Shrestha; Kyung Taec Kim
Gwangju Institute of Science and Technology, Democratic People's Republic of Korea

We perform theoretical calculations to demonstrate that single or few-cycle laser pulses can generate an intense terahertz (THz) emission by a directional current. The THz wave is strongest at the carrier-envelope phase (CEP) of 90 deg. The strength of the THz wave increases as the pulse duration decreases. The results clearly show that the THz wave is maximized when the directional current is maximized.

Mo-Po1-19
Nonlinearity In Indium Phosphide Using THz Radiation
Rakesh Kumar Vaddapally¹; Chandra vardhan Kotyada¹; Kamalesh Jana¹; Amit D Lad¹; Yash Mukesh Ved¹; Shriganesh Prabhu¹; Gottfried H Döhler²; Ravindra Kumar Gattamraju^1
1Tata Institute of Fundamental Research, India; ²Max Planck Institute for the Science of Light, Germany

Broad band Terahertz(THz) radiation has been used to study the non-linearity in semiconductor materials. The broad band source has been generated using the two color mixing technique from a 20 TW class system. The energy and intensity of the broadband terahertz source which is of the order of microjoules and MV/cm is intense enough to induce non-linearity in the semiconductor. The photon energy of the THz radiation is of the order of meV which is much less than the band gap of the semiconductor materials. Still THz radiation is able to induce nonlinear nature in Indium Phosphide semiconductor. The free carriers are scattered from lowest inter-valley of the semiconductor to the next highest inter-valley of the semiconductor in the conduction band leading to the reduction of overall conductivity of the semiconductor. Thus causing high transmission of THz showing non-linearity in the semiconductor.

Mo-Po1-20
Terahertz Generation By Two-color Laser Filamentation
Sarath Maratha Palli¹; Philipp Wustelt¹; Slawomir Skruszewicz¹; Gerhard G Paulus¹; Sergey Popruzhenko²; Amrutha Gopal^1
1Institut für Optik und Quantenelektronik, Germany; ²Prokhorov General Physics Institute, Prokhorov General Physics Institute, 38 Vavilov str., Russian Federation

Generation of broadband terahertz radiation in air by ionization using two-color femtosecond laser pulses is investigated. Terahertz pulse energy is enhanced by varying the polarization of the laser pulses. We also investigated the influence of phase shift between the femtosecond pulses on the emitted terahertz energy.

Mo-Po1-21
Second Optical Harmonic Generation From Interfaces Of Isotropic Materials In Strong Terahertz Field: Surface Vs Bulk Contributions
Sergey Bodrov¹; Michael Emelin²; Yuri Sergeev²; Alexey Korytin²; Michael Ryabikin²; Andrey Stepanov^2
1University of Nizhny Novgorod, Russian Federation; ²Institute of Applied Physics of the Russian Academy of Sciences, Russian Federation

Second optical harmonic generation by nonlinear interaction of femtosecond laser and terahertz pulses in a slab of fused quartz was investigated. It was shown that the second harmonic signal rises only near the slab surfaces and not from the bulk of the fused quartz. The theory of THz induced second optical harmonic in transparent material including dispersion of the optical radiation as well as velocity mismatch of THz and optical pulse was developed. The theory agrees well with experiment.

Mo-Po1-22
THz Generation In Laser Filament Under Electric Field Conditions
Valery Losev; Dmitrii Lubenko; Vladimir Prokopev; Sergey Alekseev; Mikhail Ivanov
IHCE SB RAS, IHCE SB RAS, Russian Federation

We present experimental results of generation THz range radiation in a laser plasma. Comparison of one and two-color optical pumping schemes are presented. We report about dependence THz radiation energy from electrical field application point to filament. The maximum generation efficiency is observed when an electric field is applied to geometrical focus point (laser filament is formed from geometrical focus point towards the laser source). The mechanisms of this effect are discussed.

Mo-Po1-23
Competition Between Positive And Negative Terahertz Photoconductivity In Variable Thickness Hg1-xCdxTe Epitaxial Layers
Alexandra Galeeva¹; Alexey Artamkin¹; Alexey Kazakov¹; Mikhail Bannikov²; Anton Ikonnikov¹; Sergey Dvoretskiy³; Nikolay Mikhailov³; Sergey Danilov⁴; Ludmila Ryabova¹; Dmitry Khokhlov^1
1M.V. Lomonosov Moscow State University, Russian Federation; ²P.N. Lebedev Physical Institute, Russian Federation; ³Rzhanov Institute of Semiconductor Physics, Russian Federation; ⁴Regensburg University, Germany

In this work, we demonstrate that the terahertz photoconductivity in Hg1-xCdxTe epitaxial films (x = 0.13 -- 0.15) is featured by superimposed positive and negative components. The dramatic drop of the positive photoresponse as the sample thickness decreases indicates the crucial role of the bulk carrier contribution to the non-equilibrium transport. However, the photoresponse behavior observed in the magnetic field applied is an argument for an edge phototransport channel formation. We discuss the sign-alternating photoconductivity kinetics in terms of the model that takes into account both the bulk electron excitation and the surface/interface states contribution.

Mo-Po1-24
Continuous Wave Microscopy Based On Solid Immersion Lens
Yesenia Angélica García Jomaso¹; Naser Qureshi²; Calos Gerardo Treviño Palacios³; Jesús Garduño Mejía²; Rafael Izazaga Pérez^3
1Universidad Nacional Autónoma de México, Mexico; ²ICAT-UNAM, Mexico; ³INAOE, INAOE, Mexico

We describe a basic approach of transmission terahertz microscopy based on solid immersion lenses. We use a Backward Wave Oscillator (BWO) as a radiation source, a hyperemispherical silicon lens as solid immersion lens and as a detector a low power pyroelectric. The experimental results show that with this approach we can improve the terahertz spot diameter size of the system compared with a simply aspherical lens. The spot diameter at the focus of the immersion lens is about 0.34 ? at 600 GHz. This approach is extended to an interferometric system to achieve a better sensitivity of the microscope.

Mo-Po1-25
Simulation Of A THz Sheet Beam Cyclotron Resonance Staggered Double Grating Traveling Wave Tube
Yu Fan; Zhiqiang Zhang
Institute of electronics, Chinese academy of sciences, China

A Y band cyclotron resonance staggered double-grating traveling wave tube (TWT) is simulated, and a sheet beam with cyclotron electrons is applied to the TWT. Simulation result of the cyclotron resonance enhancement effect is shown. Different ratios of the transverse velocity and longitudinal velocity are compared.

Mo-Po1-26
Terahertz Time-Domain Polarimetry Of Carbon Nanomaterials
Anatoly Kvitsinskiy¹; Petr Demchenko¹; Alexander Grebenchukov¹; Egor Litvinov¹; Maxim Masyukov¹; Anton Zaitsev¹; Ilya Anoshkin¹; Anna Baldycheva²; Evgeniya Kovalska²; Anna Vozianova¹; Mikhail Khodzitsky^1
1ITMO University, Russian Federation; ²University of Exeter, United Kingdom

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to study of polarization properties of a few-layer graphene (FLG) and a randomly oriented single-walled carbon nanotube (SWCNT) thin film on silicon (Si) substrates in terahertz (THz) frequency range under an external optical pumping (OP) and an external static magnetic field (MF). Frequency dependencies of azimuth and ellipticity angles of a polarization ellipse of the samples were obtained experimentally. The results confirm the fact that, based on carbon nanomaterials, it is possible to devise tunable THz polarization modulators for use in the latest security and telecommunication systems.

Mo-Po1-27
THz EMI Shielding In Graphene/PMMA Multilayers
Can Koral¹; Gianpaolo Papari²; Maria Giovanna Pastore Carbone³; Christos Pavlou³; Costas Galiotis³; Antonello Andreone^1
1INFN_National Institute of Nuclear Physics Section of Naples, Italy; ²Department of Physics, University of Naples "Federico II", Italy; ³FORTH/ICEHT Patras, Greece

The electromagnetic interference (EMI) shielding mechanisms of graphene/PMMA multilayered structures are experimentally investigated by using time domain spectroscopy (TDS) in the THz range. Stacked plates of similar thickness (~ 5μm), starting from a single layer up to 100 layers, were produced by a novel approach combining ultra-thin polymer casting and wet deposition techniques. These nano laminates show enhanced electrical conductivity (~ 100 S/cm) and superior specific shielding effectiveness (~ 2-10^4 dB cm² g^-1).

Mo-Po1-28
Tri-band Linear To Circular Polarization Converter Based On Transmissive Metasurfaces
Ayesha Kosar Fahad; CunJun Ruan; Tanveer Ul Haq; Shahid Ullah
School of Electronic and Information Engineering, Beihang University, China

Multi-band operation for terahertz wireless systems is a challenging problem. We propose a triple-band linear to circular polarization converter in the Terahertz regime using metasurfaces in transmission modes. The converter is composed of bi-layered metasurfaces separated by a dielectric spacer. Three bands (0.54-0.804, 1.904-2.476, and 2.96-3.884 THz) of linear to circular polarization conversion (LCPC) are achieved due to the superposition of the two transmitted components with a near 90Ã,° phase difference. Idea is verified by finite element method simulation and paves a way to the design of multi-band ransmissive LCPC

Mo-Po1-29
Ionic Permeability And Interfacial Doping Of Graphene On SiO2 Measured With Terahertz Photoconductivity Measurements
Hai Wang¹; Xiaoyu Jia¹; Mischa Bonn¹; Klaas-Jan Tielrooij^2
1Max Planck Institute for Polymer Research, Germany; ²Catalan Institute of Nanoscience and Nanotechnology (ICN2), Spain

Graphene has been widely used in various electrochemical applications owing to its outstanding electrical and chemical properties. The presence of electrolyte at the graphene surfaces affects graphene's electronic properties, especially its electrical conductivity. The precise mechanism underlying the graphene-electrolyte interaction has remained elusive, despite the importance of graphene for electrochemical applications. Here, we employ optical-pump THz-probe spectroscopy as a contact-free and all-optical means to investigate the impact of cations on graphene conductivity in the electrolyte. We reveal ionic permeability though graphene, resulting in an interfacial doping effect in SiO2-supported graphene.

Mo-Po1-30
Temperature Dependent Sheet Conductivity Of MoS2 Measured By Terahertz Time-Domain Spectroscopy
Tao Li; Jun Zhou; Yanshun Zheng; Zheng Zhu; Lin Zhou; Xin Rao; Jun Wang
University of Electronic Science and Technology of China, China

In this work, a typical two-dimensional (2D) material MoS2 has been measured by terahertz time-domain spectroscopy (THz-TDS), and its temperature dependent properties in the temperature range fom 120 K to 500 K have been studied. The transmittance and sheet conductivitiy of monolayer MoS2 have been obtained at different temperatures. This study is useful for the understanding of 2D materials in the THz frequency regions.

Mo-Po1-31
Transmission Properties Of Transition Metal Dichalcogenides And Modified Graphene Thin Films In Visible, NIR And THz Frequency Ranges
Maria Zhukova¹; Egor Oparin¹; Polina Shaban¹; Anton Tcypkin¹; Ben Hogan²; Evgeniya Kovalska²; Monica Craciun²; Anna Baldycheva^2
1ITMO University, Russian Federation; ²University of Exeter, United Kingdom

Here we demonstrate the transmission properties of a thin tungsten disulfide WS2 film fabricated from liquid crystal solutions in near-infrared and THz ranges. These results are compared with other transition metal dichalcogenides transferred to different substrates and unique FeCl3 intercalated graphene-based structures. The introduction of impurities, the selection of structural dimensions and the use of an appropriate substrate for modified 2D layered materials allow controlling the transmission of samples for both the terahertz and infrared ranges, which can be used for the creation of effective modulators and components for THz spectroscopy systems.

Mo-Po1-32
Strong Carrier Temperature Dependence Of Complex THz Conductivity of Photo-excited Graphene Due To Electron-phonon Coupling
Masatsugu Yamashita; Sho Ikeda; Chiko Otani
RIKEN, Japan

Ultra-broadband THz conductivities of doped monolayer graphene on PET substrate after photo-excitation at various optical pump fluence are investigated. THz conductivity corresponds to the intra-band transition of hot carriers decreases and deviates from the Drude-type frequency dependence as the pump fluence increases, indicating the broader carrier-energy distribution and energy dependent scattering. However, we found that the semi-classical Boltzmann transport theory with dominant carrier scattering mechanisms such as charged impurity and intrinsic optical phonon scattering with e-ph coupling strength from Density functional theory within GGA approximation failed to explain the hot carrier temperature dependence of THz conductivity spectra. This result suggests that the underestimation of e-ph coupling by DFT calculation and the importance of e-e interaction on the e-ph coupling

Mo-Po1-33
Intraband Ultrafast Terahertz Conductivity Dynamics In Graphene
zeyu zhang; Tingyuan Jia
Shanghai Institute of Optics and Fine Mechanics, China

Understanding the subpicosecond carrier dynamics of graphene play a crucial role in its optoelectronic allications. By using various photon energy pump, THz probe spectroscopy, the thermalization dynamics of monolayer graphene was presented. For a doped graphene, the thermal induced intraband terahertz conductivity dynamics shows typically thermal relaxation process in our experiment. The importance of the hot carrier multi-plication process of impurities scattering is discussed for graphene photodetector device applications.

Mo-Po1-34
Refractive Index Modulation Induced By High-Intensity THz Radiation
Mohammed Almassarani¹; Abel Woldegeorgis²; Takayuki Kurihara³; Amrutha Gopal^2
1Helmholtz Institute Jena, Germany; ²Institute of Optics and Quantum electronics, Germany; ³University of Konstanz, Germany

Nonlinear refractive index and absorption coefficient are measured for common semiconductor material such as silicon and organic molecule such as lactose in the terahertz (THz) spectral regime extending from 0.1 to 3 THz. THz pulses with a field strength of 440 MV/m have been employed. Transmittance and the transmitted spectra were measured using Z-scan and single shot noncollinear electro-optic pump-probe techniques. A maximum change in refractive index (Δn) of - 0.128 and +0.245 were measured in lactose and silicon, respectively.

Mo-Po1-35
THz Spatial Modulation In The Fourier Plane
Polina Stefanova; Andreas Klein; Claudio Balocco; Andrew Gallant
Durham University, Department of Engineering, United Kingdom

Application of the real-time image processing method of 4F optical systems is presented in the THz regime. Direct manipulation of the Fourier transform of an image through addressable metamaterials is to be explored, in order to achieve THz spatial modulation, beam forming and beam steering.

Mo-Po1-36
The Terahertz Near-field Response Of Graphene Layers And Graphene Structures
Valerii Trukhin¹; Ilia Mustafin¹; Sergey Lebedev¹; Anna Baldycheva^2
1Ioffe Institute, Russian Federation; ²University of Exeter, United Kingdom

We report on the experimental study of scattering and the near-field interaction of a THz electromagnetic field with graphene layers near the probe of a terahertz near-field microscope. There are resonance lines in the spectrum for a graphene monolayer-based transistor structure, which is possibly due to the strong plasmon response at terahertz frequencies and the manifestation of plasmon interference in the graphene strip.

Mo-Po1-37
Sensitivity Measurement Of Resonant-Tunneling-Diode Terahertz Detectors
Yuma Takida¹; Safumi Suzuki²; Masahiro Asada²; Hiroaki Minamide^1
1RIKEN, Japan; ²Tokyo Institute of Technology, Japan

We report on the performance characterization of resonant tunneling diode (RTD) devices as a terahertz (THz)-wave detector. The frequency-dependent sensitivity of quasi-optical RTD detectors has been calibrated by using a frequency-tunable, sub-ns pulsed THz-wave source. The 0.78-THz, slot-antenna-integrated RTD device shows the peak responsivity of 80 V/W at 0.76 THz with the full-width at half-maximum bandwidth of 70 GHz.

Mo-Po1-38
Observation Of Dirac Semi-metallic Topological State In SrIrO3 And CaIrO3 Using Terahertz Time-domain Spectroscopy
Dhanvir Rana; Santhosh Kumar K
Indian Institute of Science Education and Research (IISER) Bhopal, India

Experimental realization of quantum phases such as Dirac and Weyl semimetals, topological insulators and superconductors is an emerging subject of interest in condensed matter physics. In this talk, I will give a brief introduction to Dirac semimetals and theoretical predictions of such ground state in orthorhombic perovskite iridates having strong spin-orbit coupling. I will present the observation of such 3D Dirac semi-metallic ground state in AIrO3 (A = Ca, Sr) thin films using terahertz time-domain spectroscopy.

Mo-Po1-39
0.37 THz Gyro-TWA With A Cryo-free SCM: Design And Simulation
Craig Donaldson¹; Liang Zhang¹; Adrian Cross¹; Kevin Ronald¹; Alan Phelps¹; Wenlong He^2
1University of Strathclyde, United Kingdom; ²Shenzhen University, College of Electronic Science and Technology, China

This paper reports the work being carried out to realize a gyrotron-traveling wave amplifier operating at 372 GHz based on a helically corrugated interaction region (HCIR). The high magnetic field will be provided through a cryo-free superconducting magnet. There are many components in the waveguide circuit, which must achieve very low reflection targets. The design and simulation results of the gyro-TWA, the cusp electron beam source, the sub-millimetre wave components, as well as measurement of the HCIR will be presented in this paper.

Mo-Po1-40
Recent Results Of A CW, 94 GHz Second Harmonic Gyrotron Based On A Continuous Operation Solenoid
Dimin Sun; Tingting Zhuo; Guowu Ma; Linlin Hu; Hongbin Chen; Fanbao Meng
Institute of Applied Electronics, China Academy of Engineering Physics, China

Recent results of a CW, 94 GHz second harmonic gyrotron with a 1.8 T continuous operation solenoid are presented. The DC solenoid was cooled by water. Its inner bore diameter is 66 mm. The power consumption of the solenoid is 28 kW and the driving current is about 500 A. The gyrating electron beam was generated by a compact triode magnetic injection gun. A high efficiency internal quasi-optical mode converter with a pre-bunch quasi-optical launcher was used to separate the wave from the electron beam. The operating mode of the harmonic gyrotron is TE02. During the CW test, its operational frequency stabilized at 93.9 GHz. In the test, 5 min operation was realized. The output power is 12 kW with an electron beam of 45 kV, 1.6 A. The output efficiency is 24% with a single stage depressed collector.

Mo-Po1-41
Optimal Design Of A Magnetron Injection Gun For A 0.5 THz Continuously Frequency-tunable CW Gyrotron
Yanqing Zhang; Wei Wang; Tao Song; Jie Huang; Qiao Hu; Yichao Cao; Chen Zhang; Diwei Liu
UESTC, China

In this paper, the single anode magnetron injection gun with relatively low transverse velocity spread and high velocity pitch factor is designed for a 0.5THz continuously frequency-tunable CW gyrotron.

Mo-Po1-42
Electromagnetic Characteristics Of A Double Confocal Waveguide For A Gyro-TWT
Diwei Liu; Chen Zhang; Wei Wang; Tao Song; Qiao Hu; Yichao Cao; Yanqing Zhang
UESTC, China

There are two stable states existing in the double confocal waveguide, which are "superposition mode" and "ring mode". Compared the mode density in the double confocal waveguide with that in the single confocal waveguide and the cylindrical waveguide in the same frequency range, it is obvious that the mode density in the double confocal waveguides is relatively sparse. Hence, the double confocal waveguide has the characteristic of both mode selectivity and efficiency enhancement.

Mo-Po1-43
Study Of Low Voltage Angular Log-periodic Slow Wave Structure For 340 GHz TWT
Hexin Wang¹; Duo Xu¹; Xinyi Li²; Tenglong He¹; Zhanliang Wang¹; Ruichao Yang¹; Tao Tang¹; Zhaoyun Duan¹; Huarong Gong¹; Yanyu Wei¹; Yubin Gong^1
1University of Electronic Science and Technology of China, China; ²Nanjing Sanle Electronics Group Co., Ltd, China

A novel angular log-periodic groove waveguide slow wave structure (SWS) for 340 GHz traveling wave tube (TWT) is proposed in this paper. Due to the unique characteristics of log-periodic form, the novel SWS could achieve a very low operating voltage and small scale at the same time. By using the groove folded waveguide, the high aspect ratio fan-shaped sheet electron beam could interact with electromagnetic wave in the groove tunnel. According to direct mathematical equation, the operating voltage is 6310 V at 340 GHz and the total length of SWS is 8.6 mm, which could get an output power of 36 W with 20.7 dB gain.

Mo-Po1-44
A Novel Millimeter-wave Oversized Coaxial Relativistic Oscillator With Low Guiding Magnetic Field And High Power Capacity
Junpu Ling; Juntao He; Lili Song; Xingjun Ge; Jinchuan Ju; Bingfang Deng
College of interdisciplinary Studies, National University of Defense Technology, China

A novel Millimeter-wave oversized coaxial relativistic oscillator with low guiding magnetic field and high power capacity is proposed. The physical mechanism of this oscillator is investigated by theory and simulation. By introducing a coaxial structure and quasi body wave adopted as the operating mode, the oscillator can run stably under low guiding magnetic. Meanwhile, with an oversized structure and extended interaction extractor operating at higher order mode, the proposed oscillator has the potential of obtaining high output power close to Giggawatt-class. Main structure parameters are optimized by particle in cell simulations. Particle-in-cell simulations show that with the oversized coaxial structure, quasi body wave and extended interaction extractor operating at higher order mode, this proposed oscillator generates a 31 GHz, 840 MW microwave, while the diode voltage is 400 kV, the beam current is 6.1 kA, and the guiding magnetic field is 0.6 T. The corresponding power efficiency reaches 35%.

Mo-Po1-45
Terahertz-Infrared Spectroscopy Of Tm0.19Yb0.81B12 Dodecaboride
Elena Zhukova¹; Boris Gorshunov²; Andrey Azarevich³; Alexey Bogach³; Volodymyr B. Filipov⁴; Nataliya Yu. Shitsev⁴; Gennady A. Komandin³; Andrey V. Muratov⁵; Yuri A. Aleshchenko⁵; Nickolay E. Sluchanko^3
1Moscow Institute of Physics and Technology, Russian Federation; ²Moscow Institute of physics and technology, Russian Federation; ³Prokhorov General Physics Institute, Russian Academy of Sciences, Russian Federation; ⁴Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Ukraine; ⁵Lebedev Physical Institute, Russian Federation

First detailed measurements of terahertz-infrared electrodynamic response of high-quality single-crystalline Tm0.19Yb0.81B12 dodecaboride with dynamic charge stripes are performed at temperatures 5--300 K. Dramatic temperature changes in the dynamic conductivity spectra are observed, single-particle and collective excitations identified and their origin is discussed in terms of metal-insulator transition.

Mo-Po1-46
A Novel V-band Relativistic Transit-time Oscillator With High Power Handling Capacity
Bingfang Deng; Juntao He; Junpu Ling; Xingjun Ge; Jinchuan Ju
College of Advanced Interdisciplinary Studies, National University of Defense Technology, China

A novel V-band coaxial transit-time oscillator (TTO) with high power handling capacity is presented. The interaction region is designed to operate in TM02 mode to increase power handling capacity of the device. By using a traveling wave output structure, the saturation time of the device is improved, and the maximum surface electric field is decreased. The output structure is also good for improving beam-wave interaction. To avoid mode competition, deep corrugation is applied to the slow wave structure, so the Rayleigh hypothesis is not satisfied. Hence the dispersion relation of the SWS in output structure is analyzed by mode matching method instead of Floquet harmonic expansion method. In numerical simulation, a 642MW microwave pulse at 60.0GHz is obtained with a diode voltage of 400kV and beam current of 5kA. The power conversion efficiency is about 32.1%.

Mo-Po1-47
Development Of A 140 GHz 50kW Gyrotron In IAE
Linlin Hu; Guowu Ma; Dimin Sun; Tingting Zhuo; Qili Huang; Hongbin Chen; Fanbao Meng
Institute of Applied Electronics, China Academy of Engineering Physics, China

A 140GHz 50kWgyrotron as the first development stage in IAE-CAEP has been fabricated and tested. In the experiment, the gyrotron has achieved a reliable CW operation at 20kW for 60s, long-pulse operation at 30kW for 20s and repetitive pulse operation at 50kW for 30s with 60% duty cycle. The extension of pulse duration was hindered by the outgassing of BN window due to overheating. The results further confirmed that BN window has limited power capacity for high-frequency high-power gyrotrons. A gyrotron with a CVD diamond window has been fabricated. The experiment will be carried out in the next half of 2019.

Mo-Po1-48
Powerful Relativistic Oscillators Of THz-band Based On Excitation Of Talbot-type Supermode In An Oversized Cavity
Andrey Savilov; Yulia Oparina; Nikolai Peskov
Institute of Applied Physics RAS, Russian Federation

For relativistic oscillators, a new interaction regime is proposed based on the excitation of not a fixed transverse mode of the cavity, but a supermode formed by a fixed set of the transverse modes. Such regime is implemented in a quasi-optical cavity based on the Talbot effect, and allows to obtain narrow-band oscillation in a strongly oversized interaction space. Simulations of THz-band FEL with sub-GW to GW-level power driven by high-current relativistic electron beam are discussed

Mo-Po1-49
Investigation Of A Mini-Channel Cavity Cooling Concept For A 170 GHz, 2 MW Coaxial-Cavity Gyrotron
Stefan Illy; Konstantinos Avramidis; Philipp Bruecker; Gerd Gantenbein; Parth Kalaria; Sebastian Ruess; Manfred Thumm; John Jelonnek
Karlsruhe Institute of Technology / IHM, Germany

The maximum heat load on the cavity wall of high power fusion gyrotrons is one of the major limiting technological factors for the operation of the tube. To achieve the requested output power, efficiency and pulse length, a very efficient cooling of the interaction structure is mandatory. In this work, the performance of a mini-channel cavity cooling system for a 170 GHz, 2 MW coaxial-cavity gyrotron is numerically investigated, including the development of a mock-up test set-up for experimental validation.

Mo-Po1-50
Study On A Quasi-Optical Mode Converter For Gyrotron Based On Metamaterial
Wenjie Fu; Shijie Hu; Chaoyang Zhang; Xiaotong Guan; Yang Yan
University of Electronic Science and Technology of China, China

Artificial metamaterials offer unique functionalities for manipulating the spectral and spatial properties of electromagnetic waves in unconventional ways. In this paper, we report a transmission-type quasi-optical mode converter for gyrotron based on metamaterial. The initial simulation results show that the designed metamaterial quasi-optical mode converter is capable to transform the cylindrical TE01 mode to Gaussian beam, and the beam on the observed plane is with more than 95% scalar Gaussian mode content.

 

Mo-Po1-51
A Way To Match The Second Symmetric Mode Of Double-Grid Slow Wave Structure For Terahertz BWO
Yue Zhao¹; Hairong Yin¹; Jun Cheng¹; Yanyu Wei¹; Jin Xu¹; Lingna Yue¹; Jinjun Feng^2
1University of Electronic Science and Technology of China, China; ²Beijing Vacuum Electronics Research Institute, China

In this paper, a way to match the second symmetric mode of double-grid slow wave structure designed for a practical 1-THz terahertz backward wave oscillator is presented. Simulation results show that the return loss is less than -15 dB, and the insertion loss is about -4 dB in the 50-GHz operating bandwidth.

Mo-Po1-52
Project Of Relativistic Mm-wave Amplifier With Multi-pass Interaction
Alexander Leontyev; Edward Abubakirov; Andrey Konyushkov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

The concept of the amplifier based on double amplification of symmetrical and non-symmetrical modes in relativistic traveling wave tube (TWT) with modulating resonator is described. The input signal excites E01 mode which goes through the first pass of amplification. The hybrid HE11 mode is used for the second pass of amplification and output. The simplified model of amplifier is built and theoretical research of the amplifier operation in the Ka band was performed. It was shown that the double pass interaction can provide more than 40 dB of gain along with 30-35% operation efficiency.

Mo-Po1-53
Characteristics Of A Low-Voltage Gyrotron Backward-Wave Oscillator
Chien-Lun Hung¹; Yi-Sheng Yeh²; Tsun-Hsu Chang^3
1National Penghu University of Science and Technology, Taiwan; ²Southern Taiwan University of Science and Technology, Taiwan; ³National Tsing Hua University, Taiwan

Gyrotrons are usually operated on high voltages to generate high power coherent radiation in the millimeter to terahertz band. Recently, some high frequency applications do not require high power sources. For such applications, lowing the voltage of a gyrotron becomes an important issue. This study analyzes linear and nonlinear characteristics of a gyrotron backward-wave oscillator (gyro-BWO) operating in low voltage regime. Simulation results predict that the start-oscillation current of a gyro-BWO increases rapidly when the voltage decreases to a lower limit. Moreover, the efficiency and the tuning bandwidth of a low-voltage gyro-BWO are investigated.

Mo-Po1-54
Propagation Characteristics Of Periodic Azimuthally Corrugated Waveguides Derived By The FDTD Code COCHLEA
Dimitrios Peponis; Georgios Latsas; Ioannis Chelis; Ioannis Tigelis
National and Kapodistrian University of Athens, Faculty of Physics, Greece

Azimuthal indentations have been proposed as an additional mean to suppress the parasitic oscillations in the gyrotron stacked beam-tunnel. As a first step, a smooth waveguide with azimuthal indentations was studied using COCHLEA code in order to identify their influence on the propagation characteristics. The S- parameters were calculated on the input and the output of the structure by decomposing the field into several modes. It was found that by increasing the indentations depth the field distributions change significantly and resonant effects are observed.

Mo-Po1-55
Design And Test Of 253/527 GHz Gyrotron for Spectroscopy Applications
Grigory Denisov¹; Mikhail Morozkin¹; Andrey Fokin¹; Alexey Chirkov¹; Andrey Kuftin¹; Sergei Kornishin¹; Evgeny Tai²; Anton Sedov¹; Mikhail Proyavin¹; Alexander Tsvetkov¹; Mikhail Glyavin^1
1Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation; ²GYCOM Ltd, Russian Federation

A 527 GHz continuous-wave second harmonic gyrotron is in development at the IAP RAS jointly with GYCOM Ltd. as a microwave source for spectrometry and diagnostics of various media. We present first results of experimental measurements of this gyrotron including output power, power losses in the cavity, wave beam profile, frequency, and spectrum.

Mo-Po1-56
Out-of-Equilibrium Electrons And Record Thermionic Emission In LaB6
Elena Zhukova¹; Boris Gorshunov¹; Martin Dressel²; Gennady A. Komandin³; Mickhail Bednyakov¹; Andrey V. Muratov⁴; Yuri A. Aleshchenko⁴; Mickhail Anisimov³; Nataliya Yu. Shitsevalova⁵; Anatoliy V. Dukhnenko⁵; Volodymyr B. Filipov⁵; Vladimir V. Voronov³; Nickolay E. Sluchanko^3
1Moscow Institute of Physics and Technology, Russian Federation; ²Physikalisches Institut, Universität Stuttgart, Germany; ³Prokhorov General Physics Institute, Russian Academy of Sciences, Russian Federation; ⁴Lebedev Physical Institute, Russian Federation; ⁵Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Ukraine

To understand mechanisms of high thermionic emission of LaB6 we use infrared spectroscopy, DC resistivity and Hall-effect techniques to study conduction electrons state in LaB6 single crystals with different contents of 10B and 11B isotopes. We find that up to 70% of conduction electrons are strongly non-equilibrium due to involvement in the collective oscillations of electron density coupled to vibrations of Jahn-Teller unstable boron cage and rattling modes of La-ions. We claim that these non-equilibrium electrons determine the extraordinary low work function of thermoemission in LaB6.

Mo-Po1-57
Efficiency Enhancement Of High-Harmonic Gyrotron By Stable Excitation Of High Axial Mode In The TWT Regime
Ilya Bandurkin; Yury Kalynov; Ivan Osharin; Andrey Savilov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

The possibility of a stable excitation of a high axial mode in the traveling-wave tube regime in gyrotrons is demonstrated. Such an excitation becomes possible due to the use of a short element placed in the middle of the cavity and providing additional losses (either Ohmic losses or scattering into lower far-from-cutoff waves) for the near-to-cutoff first axial mode. This regime provides a significant efficiency enhancement in high-harmonic low-current gyrotrons.

Mo-Po1-58
Increasing The Diffraction Losses In Gyrotron Beam Tunnels For Improved Suppression Of Parasitic Oscillations
Ioannis Chelis¹; Dimitrios Peponis²; Georgios Latsas²; Ioannis Tigelis^2
1National and Kapodistrian University of Athens, Faculty of Physics, Greece; ²NKUA, Greece

High-power gyrotrons often suffer from parasitic oscillations in the compression region (beam tunnel) prior to the interaction cavity. A possible way to suppress the parasitic oscillations is to raise their starting currents by increasing the losses of the structure. In the present contribution we focus on the diffraction losses of the stacked copper-ceramic beam-tunnel concept. Parametric simulations show that the diffraction losses can be significantly increased by optimizing the geometric characteristics of the structure.

Mo-Po1-59
Wide Range Stepwise Frequency Tuning In Gyrotrons With Strong External Reflections
Irina Zotova¹; Naum Ginzburg¹; Andrey Malkin¹; Roman Rozental¹; Alexander Sergeev¹; Mikhail Glyavin¹; Seitaro Mitsudo²; Toshitaka Idehara^2
1Institute of Applied Physics RAS, Russian Federation; ²Research Center for Development of Far-Infrared Region, University of Fukui, Japan

We demonstrate that in a gyrotron with strong external reflections, frequency jumping in a wide range is possible due to sequential excitation of axial modes in the gyro-TWT regime. Within the frame of a time-domain model, the frequency tuning in the range of 202.3-206 GHz and the output power of 0.5 kW is shown, when modes with a number of axial variations from 1 to 10 are excited. The obtained parameters are suitable for the positronium spectroscopy in a Fabry-Perot resonator.

Mo-Po1-60
Design Of A Quasi-optical Mode Converter For A Dual-frequency Coaxial-cavity Gyrotron
Jianbo Jin; Gerd Gantenbein; Tobias Ruess; Manfred Thumm; John Jelonnek
Karlsruhe Institute of Technology / IHM, Germany

A quasi-optical mode converter is under development for an 170/204 GHz coaxial-cavity gyrotron at KIT, which is operated in the TE34,19 mode at 170 GHz and the TE40,23 mode at 204 GHz. A mirror-line launcher should be used for such modes with the ratio of caustic to launcher radius to be approximately 0.32. The optimum value of the launcher radius has been found to provide RF beams with relative high Gaussian-mode contents for both operation modes.

Mo-Po1-61
Linear Analyses Of A 0.22 THz Confocal Waveguide Gyro-TWT
Jie Yang¹; Shouxi Xu²; Yong Wang^2
1University of Chinese Academy of Sciences, China; ²Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, China

Confocal waveguide gyrotron traveling wave tube (gyro-TWT) is a novel gyrotron amplifier which can operate in higher order modes and generate high power. In this paper, the linear theory derived from kinetic theory is presented to analyze a 0.22-THz confocal waveguide Gyro-TWT which operates at HE06 mode. The linear gain is 9.6 dB/cm at 220.2 GHz. Different parameters are pointed out to show their influences on critical current of absolute instability.

Mo-Po1-62
Theoretical Research On 300GHz Carbon Nanotube Cold Cathode Gyrotron
Lulu Shao¹; Xuesong Yuan¹; Weifeng Li¹; Yu Zhang²; Bin Wang¹; Hailong Li¹; Yang Yan^1
1University of Electronic Science and Technology of China, China; ²Sun Yat-Se University, China

A 300 GHz carbon nanotube cold cathode TE03 gyrotron has been studied in this paper. Carbon nanotube cold cathode gun is optimized. Simulation results show that the average output power of 148 W has been obtained. This gyrotron experiment will be performed based on these parameters in the future.

Mo-Po1-63
Using Reflections For Suppressing Parasitic Oscillation In A Multimode Gyrotron
Maria Melnikova¹; Asel Adilova¹; Nikita Ryskin^2
1Saratov State University, Russian Federation; ²Saratov Branch, Institute of Radio Engineering and Electronics, RAS, Russian Federation

In recent years, the problem of control of gyrotron radiation by partial reflection of the output power from a remote load has attracted a considerable interest. In this paper, we study a reflection influence on mode-competition scenario in a multimode gyrotron. A possibility of controlling the mode competition processes by proper adjustment of reflection factors for different modes is discussed.

 

Mo-Po1-64
Simulations Of Sub-THz Confocal-Cavity Gyrotrons With Different Configurations Of Electron Beams
Mikhail Glyavin; Vladislav Zaslavski; Vladimir Manuilov; Irina Zotova; Dmitry Sobolev
Institute of Applied Physics Russian Academy of Sciences (IAP RAS), Russian Federation

Based on 3D PIC (particle-in-cell) simulations, we conduct a comparative analysis of operation of sub-THz confocal-cavity gyrotrons with two configurations of a driven electron beam namely, a conventional cylindrical hollow electron beam and a sheet rotating electron beam injected midway between the cavity mirrors. It is demonstrated, that for parameters of the experimentally realized 140 GHz confocal gyrotron, the starting and operating current can be significantly decreased with using the sheet rotating electron beam, while the efficiency of generation increases at least in 1.5 times (up to 30-35%). The smooth frequency tuning of 5% by mechanical variation of the distance between mirrors are also demonstrated.

Mo-Po1-65
Development Of 100 MW W-Band Gyrotron With Relativistic Sheet Electron Beam
Naum Ginzburg¹; Andrey Malkin¹; Roman Rozental¹; Vladislav Zaslavsky¹; Ilya Zheleznov¹; Vladimir Tarakanov^2
1Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation; ²Moscow Engineering Physics Institute, Russian Federation

Based on 3D PIC-simulations we study a possibility of development of a high-power W-band gyrotron driven by a sheet large-aperture relativistic electron beam. Improvement in selectivity can be provided by using a planar cavity, which is partially open over transverse (with respect to a beam motion) direction. It was demonstrated that for 500 keV/1 kA electron beam with the transverse size of ten wavelengths, a single-mode generation with 100 MW output power and efficiency of 20% can be obtained in the considered scheme.

Mo-Po1-66
Development Of Powerful W-band Planar Surface-Wave Oscillator Driven By High-Current Relativistic Sheet Electron Beam
Nikolai Peskov¹; Andrey Arzhannikov²; Naum Ginzburg¹; Petr Kalinin²; Tatiana Krapivnitskaya¹; Eugene Sandalov²; Alexander Sergeev¹; Stanislav Sinitsky²; Vasily Stepanov²; Vladislav Zaslavsky^1
1Institute of Applied Physics RAS, Russian Federation; ²Budker Institute of Nuclear Physics RAS, Russian Federation

Project of powerful planar W-band surface-wave oscillator is under development in collaboration between IAP RAS (N.Novgorod) and BINP RAS (Novosibirsk) at the "ELMI" accelerator 1 MeV / 5 - 7 kA / 3 ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,µs. Electrodynamic system of this oscillator is based on a two-dimensional doubly-periodical structure, which combines properties of a slow-wave system that realizes conditions for an effective Cherenkov interaction with a high-current rectilinear sheet electron beam, and a high-Q resonator that implements mechanism of two-dimensional distributed feedback and provides selective excitation of the operating mode in the strongly oversized interaction space. Design parameters of the project are discussed and results of the simulations are presented, which demonstrate possibility to achieve in the considered scheme a stable narrow-band regime of oscillation with output power of the gigawatt level.

Mo-Po1-67
Spectral Radiation Pattern Of Bulk Waves Emitted By Thermally Stimulated Surface Plasmons At The Sample Edge
Ildus Khasanov¹; Alexey Nikitin²; Vasily Gerasimov^3
1Scientific and Technological Center of Unique Instrumentation of the Russian Academy of Sciences, Russian Federation; ²Scientific and Technological Center for Unique Instrumentation of RAS, Russian Federation; ³Budker Institute of Nuclear Physics SB RAS, Russian Federation

It was shown that the edge of a metal body face emits narrowly directed IR radiation with a spectrum of blackbody type, due to the surface plasmon nature of this radiation. Here we present the results of studies showing that the direction of the radiation pattern depends on its spectral composition. This confirms applicability of the analytical model for the diffraction field of monochromatic surface plasmon-polaritons (SPPs) to the case of broadband TSPPs.

Mo-Po1-68
High-Efficiency Gyrotron With Beam Energy Recovery
Oleg Louksha; Pavel Trofimov
Peter the Great St. Petersburg Polytechnic University, Russian Federation

This paper presents results of the combined 3-D simulation of a 74.2 GHz, 100 kW gyrotron with a four-stage depressed collector. The maximum overall efficiency of 72 % has been achieved as a result of improvement of electron beam quality and effective recovery of spent beam energy.

Mo-Po1-69
Compact Pulsed Magnets Designed For An 800 GHz, 2th Harmonics Gyrotron
Pengbo Wang¹; Houxiu Xiao¹; Donghui Xia²; Xin Qi¹; Liang Li¹; Xiaofeng Li¹; Xianfei Chen^1
1Huazhong University of Science and Technology, Wuhan National High Magnetic Field Center, China; ²Huazhong University of Science and Technology, School of Electrical and Electronics Engineering, China

This paper proposes the design of compact pulsed magnets for high frequency gyrotrons. With 12 layers of helices reinforced by zylon fibers, the pulsed magnet provides a magnetic field of 14.8 T for the 800 GHz gyrotron operating at the second harmonics. The pulse duration can be as much as 165 ms, and a pitch factor of 1.32 and a transverse velocity spread of 5.12% were obtained with the given electron gun geometry.

Mo-Po1-70
Design Of Quasi-Optical Mode Converter For 28GHz Gyrotron
Qili Huang; Dimin Sun; Linlin Hu; Tingting Zhuo; Guowu Ma; Hongbin Chen
Institute of Applied Electronics, China Academy of Engineering Physics, China

This paper presents the design of two quasi-optical mode converter for gyrotrons to transform the cavity waveguide mode TE02 and TE83 into a fundamental Gaussian beam. Those two quasi-optical mode converters are optimized by a combination of three methods, which are the scalar diffraction theorem, the K-S phase-correcting optimization iterative algorithm, and Geometrical Optics. According to the results, the conversion efficiency of energy is 92.5%( TE02) and 95%( TE83) and the Gaussian content of the output beam on the window surface is 99%.

Mo-Po1-71
Performance Tests Of ITER Gyrotrons And Design Study Of Dual-frequency ITER Gyrotron
Ryosuke Ikeda; Ken Kajiwara; Taku Nakai; Takayuki Kobayashi; Masayuki Terakado; Koji Takahashi; Keishi Sakamoto
National Institutes for Quantum and Radiological Science and Technology, Japan

Performance tests for two ITER gyrotrons have being carried out in the QST. In the tests, the output power of 1.05 MW with efficiency of 50.5 % for 300 s, the output power of 0.9 MW for 60 s in the 5 kHz full-modulation, and operation reliability of more than 90 % were achieved. Design study of dual-frequency gyrotron has been carried out to apply plasma operations at 1.8 T, 2.65 T and 5.3 T in ITER. It succeeded in design values of power transmission efficiencies in 104 GHz and 170 GHz oscillations almost equivalent to the design value in the current ITER gyrotron.

Mo-Po1-72
Double-Anode Sheet-Beam Electron Gun With A Circular Cathode For 220 GHz TWT
Shengkun Jiang¹; Zhaoyun Duan¹; Guang Yang¹; Tao Tang¹; Zhanliang Wang¹; Huarong Gong¹; Yubin Gong¹; Ye Tang²; Pan Pan²; Jun Cai²; Jinjun Feng^2
1School of Electronic Science and Engineering, University of Electronic Science and Technology of China, China; ²National Key Laboratory of Science and Technology on Vacuum Electronics in Beijing, Beijing Vacuum E, China

A 220 GHz double-anode sheet-beam electron gun with a circular cathode is designed using the three-dimensional particle simulation software Opera 18R2. The simulated results of beam current and the size of the beam waist are 140 mA and 0.5 mmÃfÆ'ââ,¬"0.1 mm at z=9 mm, respectively. This proposed double anode sheet beam electron gun is used in a T-shape staggered double-grating traveling wave tube (TWT).

Mo-Po1-73
TM-Mode Gyrotrons
Tsun-Hsu Chang
Department of Physics, National Tsing Hua University, Taiwan

Transverse magnetic (TM) waveguide modes have long been considered as the unsuitable modes for the operation of the electron cyclotron maser (ECM). This study reveals that certain TM modes might be suitable for gyrotrons --- ECM based devices. Unlike transverse electric (TE) modes, the linear behavior of the TM modes depends on the sign of the wave number kz. The negative kz has much stronger linear efficiency than that of the positive kz. In addition, the non-linear calculation for a fixed field profile shows that the efficiency of some TM modes could be as high as that of the TE modes. The current findings are encouraging and imply that TM modes might be advantageous to the gyrotron backward-wave oscillators.

Mo-Po1-74
Research On Y-Band Double Grating Diffraction Radiation Oscillators
Yaming Chen; Yaxin Zhang; Yilin Pan; Hexin Wang; Kaicheng Wang; Zhanliang Wang; Yubin Gong
University of Electronic Science and Technology of China, China

An open resonance systems (ORS) composed of cylindrical mirror and planar mirror was combined with double comb gratings, which was investigated in this paper. The results show that in such structure the electron beam will interacts with the quasi-optical mode in the cavity efficiently. The output power can reach to more than 3 W at 0.33 THz with about 2 GHz band width. This radiation system provides a potential way to develop high power and compact THz sources.

Mo-Po1-75
Study On The Beam-wave Interaction In A 28GHz Gyrotron With Complex Cavity
Yanwei Lu; Sheng Yu; Zhipeng Wang; Tianzhong Zhang; Rutai Chen; Wenjing Huang; Jin Luo
University of Electronic Science and Technology, China

In this paper, a 28GHz gyrotron with gradually tapered complex cavity is simulated and designed. In order to achieve high efficiency, we analyse the influences of the structural parameters on interaction efficiency, the effects of the electron beam parameters are also analyzed. The simulation results shows that the designed gyrotron can obtain output power of 43.18kW when the beam current is 2.1A, beam voltage is 53kV. The corresponding efficiency can reach to 38.80%.

Mo-Po1-76
Study On Hollow Cavity Of 140-GHz Gyrotrons
Yichi Zhang¹; Bentian Liu^2
1Beijing Vacuum Electronics Research Institute, China; ²National Key Laboratory of science and technology on Vacuum Electronics, China

To design an hollow cavity of 140-GHz Gyrotron, we conducted a study for TE22,6 mode cavity. Through changing magnetic field strength, voltage, current, radius and length of cavity, we analyzed the influence factors of structural parameters and electrical parameters on working performance. Under the experimental conditions of voltage 70kV and current 35A, we got a result which approximately the same with output power in fact.

Mo-Po1-77
Analysis On Resonator Coupling Characteristics Of Sub-THz EIA
Qinqin Yuan; Ziqiang Yang; Zongjun Shi; Ting Zhang; Xiaopin Tang; Feng Lan
Terahertz Science Cooperative Innovation Center, University of Electronic Science and Technology, China

The resonator coupling characteristics of Sub-THz extended interaction amplifier (EIA) with the grating and sub-wavelength hole array structure is simulated at the TM31-2π mode. Zero-field points of TM31-2π modes at the center of the beam tunnel promote an effective beam-wave interaction. The operating frequency of the intermediate cavity is 231.28 GHz with characteristic impedance of 207.74 Ω. The return losses of the input and output cavity are both better than 11.32 dB at 231.1 GHz, and the -3 dB bandwidth is 984 MHz.

Mo-Po1-78
Multiphonon Anharmonicity In MgO An Ionic Binary Compound
Paola Giura¹; Lorenzo Paulatto²; Daniele Antonangeli²; Fei He²; Ricardo P. S. M. Lobo³; Eugenio Calandrini²; Alexei Bosak⁴; Luigi Paolasini^4
1Sorbonne-University, France; ²IMPMC Sorbonne university, UMR CNRS 7590, France; ³ESPCI, LPEM, France; ⁴ESRF, France

The anharmonic lattice dynamics of MgO has been studied at ambient conditions and at high temperatures by infrared spectroscopy combined with density functional perturbation theory calculations. The agreement between the measured phonon energies and widths with ab-initio calculated values provides a direct and pertinent test of the validity of advanced theoretical methods. Long observed anharmonic features in the infrared reflectivity find a clear explanation in terms of well-defined multi-phonons scattering processes and lattice dynamics peculiarities, also responsible of a significant and sharp reduction of the longitudinal optical phonon lifetime at critical finite wave vectors. Our work highlights the importance of multi-phonons scattering processes on collective dynamics and related material properties

Mo-Po1-79
Pulsed Gyrotron Start-up Scenario In Presence Of Voltage/Current Surge Front
Yulia Novozhilova¹; Nikita Ryskin²; Mikhail Glyavin¹; et al^1
1Institute of Applied Physics RAS, Russian Federation; ²Branch, Kotel'nikov Institute of Radio Engineering and Electronics RAS, Russian Federation

The possibility of high-efficiency single-mode regimes in a sub-megawatt power 250-GHz gyrotron, which is developed for the DEMO project, is studied. Nonlinear mode interaction at the front of accelerating voltage pulse/current is discussed. It is shown that for these scenarios a single-mode high-efficiency regime is possible within a fairly broad band of cyclotron frequency mismatch. Stability of such a regime with respect to the excitation of spurious modes is studied.

Mo-Po1-80
Powerful 1 THz Third-Harmonic Gyrotron For Plasma Applications
Yuriy Kalynov; Ilia Bandurkin; Vladimir Manuilov; Ivan Osharin; Andrey Savilov; Nikolai Zavolsky
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

The possibility of creating a third-cyclotron-harmonic large-orbit gyrotron with a radiation frequency of 1 THz and an output power of several kilowatts for its use in promising plasma studies is studyed.

 

Mo-Po1-81
Competition Of Oscillations At Different High Cyclotron Harmonics In The Sub-THz Large-Orbit Gyrotron
Yuriy Kalynov; Ivan Osharin; Andrey Savilov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

Recently, 30 keV/0.7A CW sub-THz large-orbit gyrotron have been experimentally realized. Two different modes at different (second and third) cyclotron harmonic were excited in the same cavity separately at slightly different magnetic fields. This work is dedicated to description of various regimes of competition of the two modes observed in the experiment.

Mo-Po1-82
1.0 THz BWO Based On Novel Helical Groove Rectangular Waveguide
Zhigang Lu; Ruidong Wen; Zhicheng Su; Weihua Ge; Tao Tang; Huarong Gong; Yubin Gong
University of Electronic Science and Technology of China, China

A novel helical groove rectangular waveguide slow wave structure (HGRW-SWS) is put forward to develop the lower operating voltage and high electron efficiency terahertz backward wave oscillator (BWO). The major advantage of the HGRW structure is its higher interaction impedance, lower ohm loss and lower operating voltage with respect to the typical SWSs such as folded waveguide SWS or double staggered grating SWS especially in the case of higher spatial harmonics. It is found that this kind of SWS can be operating on the n=-2 harmonic with the interaction impedance of more than 1.5 ohms from the analysis of the cold characteristics of the HGRW-SWS. Moreover, the beam-wave interaction results indicate that the BWO based on the HGRW SWS can produce the output power exceeding 0.657 W in the frequency range from 0.894 THz to 1.164 THz.

Mo-Po1-83
Two-dimensional Particle Simulation Analysis Of Ion Noise In TWT
Zhixin Yang; Zugen Guo; Rujing Ji; Zhigang Lu; Zhaoyun Duan; Yubin Gong; Huarong Gong
National Key Laboratory of Science and Technology on Vacuum Electronics, University of Electronic Science and Technology, China

In this paper, we establish a calculable TWT model to analyze the ion noise and adopt the intensity of fluctuation frequency and amplitude of ions and the average kinetic energy of electrons to indicate the strength of ion noise. The relationship between ion noise and the magnetic field is discussed. An effective way to suppress ion noise is adjustment of the magnetic field so that the interaction length is an integral multiple of the scalloping wavelength, decrease the accumulation of ions. The simulation results are consistent with the theoretical analysis.

Mo-Po1-84
Design Of Electron Optical System For 0.22THz Folded Waveguide TWT
Zugen Guo; Zhixin Yang; Rujing Ji; Ping Han; Lu Zhigang; Yubin Gong; Huarong Gong; Zhanliang Wang; Tao Tang
University of Electronic Science and Technology of China, School of Electronic Science and Engineering , China

An electron optical system(EOS) of 0.22THz folded waveguide travelling-wave tube (FW-TWT) was designed in this paper. The design process of Pierce gun and periodic permanent magnet focusing system was introduced in detail. The electromagnetic field simulation software Opera-3D was used to simulate and optimize the magnetic field. This simulation results show that the electron optical system transmitted beam current 33mA, cathode voltage -19kV, the first anode -3kV, and the beam transmission rate was 100%.

 

Mo-Po1-85
Analysis Of Folded Waveguide TWT With Non-Central Double Beams
Duo Xu¹; Wei Shao¹; Tenglong He¹; Hexin Wang¹; Zhanliang Wang¹; Zhigang Lu¹; Huarong Gong¹; Zhaoyun Duan¹; Jinjun Feng²; Yubin Gong^1
1University of Electronic Science and Technology of China, China; ²Beijing Vacuum Electronics Research Insitute, China

In order to increase the output power of the folded waveguide (FW) Traveling wave tube (TWT), a novel Non-Central double beams (NCDB) FW-TWT is proposed in this paper. Compared with the traditional central beam (CB) FW-TWT, the NCDB-FW-TWT can double the output power without increasing the current of the single beam. A W-band NCDB-FW-TWT is designed in this paper. The PIC simulation results show that the maximal output power can reach 90 W and the 3-dB over 8.8%.

Mo-Po1-86
Cusp Electron Gun With Modulation Electrode For A THz Gyro-amplifier
Liang Zhang¹; Craig Donaldson²; Wenlong He³; Alan Phelps⁴; Adrian Cross^1
1University of Strathclyde, United Kingdom; ²Department of Physics, University of Strathclyde, United Kingdom; ³Shenzhen University, College of Electronic Science and Technology, China; ⁴University of Strathclyde, Department of Physics, United Kingdom

A terahertz gyrotron traveling wave amplifier (gyro-TWA) centered at 370GHz is under development for the electron paramagnetic resonance (EPR) imaging application. This paper reports the investigation of a triode-type cusp electron gun for the terahertz gyro-TWA. The simulation results showed that at the beam alpha (the ratio of transverse to axial velocity) center of 1.07, an optimal alpha spread of ~10% was achieved, when it was operated at a beam voltage of 50 kV and a beam current of 0.35 A.

Mo-Po1-87
Possibilty of Super-Radiance At The Frequencies Of 3-5 THz From Short Electron Bunches Moving In Micro-Ondulators
Nezah Balal; Vladimir L. Bratman; Yuri Lurie
Ariel University, Israel

An available frequency range of coherent radiation from ps bunches with high charge can be significantly enhanced if one uses a micro-undulator with a high transverse field. Such an undulator with a helical symmetry can be implemented by redistributing a strong uniform magnetic field by a helical ferromagnetic insertion. Simulations demonstrate that using such undulators with period of 8-10 mm enable efficient coherent spontaneous radiation from short bunches with durations of (0.08-0.15) ps and super-radiance from extended bunches with duration of about 2 ps in frequency range of 3-5 THz.

Mo-Po1-88
Experimental Results Of Spectral And Imaging From Tunable Coherent Terahertz Radiation
Xuling Lin¹; Jianbing Zhang²; Zhimin Dai²; Zhi Zhang^1
1Beijing Institute of Space Mechanics and Electricity, China; ²Shanghai Institute of Applied Physics, Chinese Academy of Sciences, China

In this paper, we demonstrate the generation and observation of watt-level, coherent tunable terahertz radiation from relativistic femtosecond electron beam. Spectral content of the coherent terahertz emission from the undulator and dipole magnet is measured, and high quality terahertz imaging experimental is carried utilizing methodology of super-resolution reconstruction.

 

Mo-Po1-89
Studying Mechanical Properties And Phase Transitions Of Aspirin Polymorphs With Terahertz Spectroscopy And Ab Initio Simulations
Qi Li¹; Andrew Bond²; Axel Zeitler^1
1University of Cambridge, United Kingdom; ²University of Cambridge, Department of Chemistry, United Kingdom

Subtle structural differences and comparable lattice energies have triggered controversial discussions on the stabilities, mechanical properties and further comparisons between two polymorphs of aspirin. In this study, terahertz time-domain spectroscopy (THz-TDS) is coupled with density functional theory (DFT) and ab initio molecule dynamics (AIMD) calculations to seek physical insight into the properties of crystalline aspirin. Large-size supercells incorporating defects are used to simulate disorder in the aspirin crystal structure to investigate possible mechanisms for polymorphic transformation. THz-TDS of aspirin single crystals is performed to investigate certain interesting modes that may play a critical role in the phase transitions and mechanical properties of aspirin.

Mo-Po1-90
Anisotropic MagnetoResistance Of 3d Ferromagnetic Metals Observed by THz-TDS
JiHo Park¹; Soo gil Lee¹; Jeong Mok Kim²; Nyun Jong Lee³; Sanghoon Kim³; Byong Guk Park²; Kab Jin Kim^1
1Department of Physics, KAIST, Republic of Korea; ²Department of Materials Science and Engineering, KAIST, Republic of Korea; ³Department of Physics, University Of Ulsan, Republic of Korea

Electrical resistance of magnetic materials depends on magnetization orientation of the sample. The representative example is anisotropic magnetoresistance (AMR)[1]. Despite a number of experimental reports, our understanding on the microscopic origin of AMR is still far from complete. Theory has predicted that the AMR originates from different electronic scattering from conduction s,p and d bands to localized d band [2] which is closely related to spin orbit coupling (SOC). However, the microscopic mechanism underlying the scattering process is yet to be fully understood experimentally. Therefore, a direct measurement of electron scattering is important for revealing the origin of AMR. Using THz-TDS, here we directly access the scattering time of conduction electron in 3d metallic ferromagnets.

Mo-Po1-91
Tilted-Pulse-Front Pumped Plane-Parallel LiNbO3 Slab THz Source
Priyo Nugraha; Gergo Krizsan; Csaba Lombosi; Laszlo Palfalvi; Gyorgy Toth; Gabor Almasi; Janos Hebling; Jozsef Fulop
Institute of Physics, University of Pecs, Hungary

A new type of tilted-pulse-front pumped terahertz (THz) source has been demonstrated, which is based on a LiNbO3 plane-parallel slab with an echelon structure on its input surface. The use of a plane-parallel nonlinear optical crystal slab enables straightforward scaling to high THz pulse energies and the production of a symmetric THz beam with a uniform pulse shape for good focusability and high field strength.

Mo-Po1-92
Terahertz Plasmonic Photocurrents In Graphene Nanostructures
Viacheslav Popov; Denis Fateev
Kotelnikov Institute of Radio Engineering and Electronics, Russian Federation

The theory of plasmon detection of terahertz radiation in a periodic graphene structure with spatially inhomogeneous graphene near the Dirac point is developed.

 

Mo-Po1-93
Development Of The Second Harmonic 190 GHz Gyrotron For OAM Communication
Ashwini Sawant; Ingeun Lee; Mun Seok Choe; EunMi Choi
Ulsan National Institute of Science and Technology (UNIST), Republic of Korea

We presented the design of a 190 GHz second harmonic gyrotron capable of generating few kWs of power in a mode-pair TE8,3 and TE11,2 at 33 and 37 kV voltage respectively. Conventional cavity with two sinusoidal perturbations has been used to reduce the mode competition from fundamental mode. It is designed for the conceptual study of OAM communication using gyrotron mode.

Mo-Po1-94
Design And Fabrication Of A D-Band Traveling Wave Tube For Millimeter Wave Communications
Rupa Basu; Laxma Billa; Jeevan Rao; Rosa Letizia; Claudio Paoloni
Lancaster University, United Kingdom

The design and fabrication aspects of a novel D-band (141 GHz-148.5 GHz) Traveling Wave Tube (TWT) for enabling the first point to multipoint front end at D-band, objective of European Commission H2020 ULTRAWAVE is presented. The ULTRAWAVE system will provide unprecedented wireless area capacity over wide area sectors, with radius up to 500 - 600 m for the future 5G high density small cell deployment. The design and fabrication processes adopted for the TWT are focused to find new low cost solutions for TWTs at millimetre waves to satisfy the requirements of the wireless market. The proposed TWT will provide more than 10 W saturated output power for achieving more than 100 Gb/s/km2 of area capacity over 600 meters radius wide angle sector, with 99.99% availability in ITU zone K.

Mo-Po1-95
Development Of High-Harmonic CW Gyrotron With An Operating Frequency Of 1.2 THz
Alexander Tsvetkov¹; Vladimir Manuilov¹; Irina Zotova¹; Ilya Bandurkin¹; Alexey Fedotov¹; Vladislav Zaslavsky¹; Yoshinori Tatematsu²; Seitaro Mitsudo²; Toshitaka Idehara²; Mikhail Glyavin^1
1Institute of Applied Physics RAS, Russian Federation; ²Research Center for Development of Far-Infrared Region, University of Fukui, Japan

The report is devoted to development of a 3d harmonic CW gyrotron with the record output frequency of 1.2 THz. Based on analyses of start currents we demonstrate, that improvement of mode selectivity can be achieved due to interaction with an electron beam having a specially increased (up to 30-40%) velocity spread. In such conditions the start current of a near-cutoff operating mode decreases due to influence of "slow" electron fractions in the electron beams. At the same time, the start currents of parasitic modes, which are very sensitive to the velocity spread, increases significantly. The suppression of spurious mode and selective excitation an operating TE15,6 mode is demonstrated in the frame of 3D particle-in-cell simulations using CST STUDIO SUITE.

Mo-Po1-96
The Effect Of The Lossy Material On The Modes In A Smooth Metallic Dielectric Loaded Gyrotron Beam Tunnel
George Latsas¹; Ioannis Tigelis¹; Jeremy Genoud²; Stefano Alberti^2
1National and Kapodistrian University of Athens/ Faculty of Physics, Greece; ²École Polytechnique Fédérale de Lausanne, Swiss Plasma Center, Switzerland

The effect of the dielectric material on the dispersion properties and behavior of the modes in a smooth metallic gyrotron beam tunnel, partially filled with a lossy dielectric material, is studied. Two kinds of modes were identified, one located inside the empty region and the other inside the dielectric region. It was seen that these two kinds of modes are not equally affected by the changes in the geometry and dielectric characteristics.

Mo-Po1-97
Design Of An 800GHz Gyrotron
Xianfei Chen; Houxiu Xiao; Tao Peng; Donghui Xia; Xin Qi; Pengbo Wang
Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, China

The design of an 800GHz gyrotron with output power of 172kW is presented. This gyrotron operates at fundamental resonance with a 30T pulsed magnet. The parameters are optimized according to the normalized parameters. The simulation results show that the maximum efficiency of 43% can be reached.

Mo-Po1-98
Experimental Study Of The Emission Properties Of Magnetron Injection Guns For High-Power Gyrotrons
Zisis Ioannidis; Tomasz Rzesnicki; Ioannis Pagonakis; Gerd Gantenbein; John Jelonnek
Karlsruhe Institute of Technology, Germany

The quality of the electron beam generated by a magnetron injection gun (MIG) is very important in order to ensure the excellent performance of high-frequency, high-power gyrotrons. A diagnostic device, operating at scaled down parameters, was recently developed at KIT in order to study the emission properties of various MIGs that are used with prototype modular short-pulse gyrotrons. Herein, we present the first experimental results that were obtained for electron guns that are used with coaxial 2 MW, 170 GHz gyrotrons.

Mo-Po1-99
Electrically-controlled THz Emission From AlGaN/GaN/Al2O3 High Electron Mobility Transistor Structures At A Temperature Of 20 K
Ignas Grigelionis¹; Pawel Prystawko²; Irmantas Kasalynas^1
1Center for Physical Sciences and Technology, Lithuania; ²Institute of High Pressure Physics UNIPRESS, Poland

We investigated radiative phenomena contributing to the THz emission of AlGaN/GaN high electron mobility transistor (HEMT) structures grown on sapphire substrate. Electrically controlled emission spectroscopy was performed in the frequency range 100-600 cm-1 at a temperature of 20 K. The electroluminescence from nitrogen vacancies in GaN buffer layer contributed to the THz emission spectrum, and the amplitude and frequency of the observed narrow emission lines were controlled by applied voltage.

Mo-Po1-100
Electric Dipole-free Meta-cylinders
Mahdi Safari¹; Ali Momeni²; Ali Abdolali²; Nazir P. Kherani^1
1Department of Electrical and Computer Engineering, University of Toronto, Canada; ²Department of Electrical Engineering, Iran University of Science and Technology, Iran

In this paper, we propose a novel asymmetrical meta-atom for control of electromagnetic wave based on analytical formulation. Here, we show that the proposed meta-cylinder is flexible and well capable of achieving exotic electromagnetic responses.

 

 

Tuesday 3 September 2019

 

09:00-10:30 - Plenary Sessions - Amphi Lavoisier

Chairperson: Jean-Louis Coutaz

09:00 Tu-Pl-1

TeraHertz Josephson Plasmonics: Controlling Supercurents in Cuprates

Andrea CAVALLERI, Max Plank Institute, Structure and Dynamics of Matter, Germany

09:45 Tu-Pl-2

Building Blocks And Concepts For THz Remote Sensing And Communications

Daniel DOLFI, Thales Research & Technology, France

10:30-11:00 - Coffee Break

11:00-12:30 Parallel sessions Tu-AM

11:00-12:30 - Tu-AM-1 - Gyrotron 4 - Amphi Lavoisier

Chairperson: Manfred Thumm

11:00 Tu-AM-1-1
Gyro-TWTs With Helically Corrugated Waveguides: Overview Of The Main Principles
Grigory Denisov; Alexander Bogdashov; Igor Gachev; Sergei Samsonov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

An overview of the main principles of operation and design for major components of the gyrotron travelling-wave tube (gyro-TWT) based on a helically corrugated waveguide is presented

11:30 Tu-AM-1-2
Recent Progress In K-band Technological Gyrotrons Development
Mikhail Glyavin¹; Mikhail Proyavin¹; Vladimir Manuilov²; et al^1
1Institute of Applied Physics RAS, Russian Federation; ²NNSU, Russian Federation

The overview of recent results and trends of the development of K-band (24-30 GHz) technological gyrotrons are given. The high-efficient second harmonic CW gyrotrons with output power up to 15 kW has been developed and tested. It is shown that promising technologies needs power increasing up to several tens kW. Due to the problem of suppression of high harmonics by fundamental one, the project of powerful CW first harmonic gyrotron is proposed. The reduction of total power consumption is realized by the magnetic system shielded by ferromagnetic screens. The report presented the 28 GHz CW technological gyrotron with the output power 25-30 kW and total (including the power consumption of the main coil) efficiency 35%. The characteristic features of the magnet, electron beam optics and electrodynamics system are described.

11:45 Tu-AM-1-3
Frequency-Tunable Reflective Gyro-BWO
Cheng-Hung Tsai¹; Tsun-Hsu Chang¹; Yoshinori Tatematsu^2
1Department of Physics, National Tsing Hua University, Taiwan; ²Research Center for Development of Far-Infrared Region, University of Fukui, Japan

We design and fabricate a novel electron gun and conduct an experiment using a tapered structure for the reflective gyrotron backward-wave oscillator (gyro-BWO). The electron gun and the interaction structure provide an ideal beam-wave coupling which enhances the interaction efficiency over a broad bandwidth. The cutoff section and mild tapers in the cavity region help to generate the 203 GHz waves operating at TE02 mode with the peak power efficiency of 30% and a wide bandwidth of 8.5 GHz. Preliminary experimental results will be reported.

12:00 Tu-AM-1-4
Broadband Terahertz Frequency Comb Generation From Guided Mode Resonance Excited By Fast Electrons
Tao Zhao; Min Hu; Renbin Zhong; Diwei Liu; Zhunhua Wu; Sen Gong; Shenggang Liu
University of Electric Science and Technolgy of China, China

A physical mechanism of generating tunable terahertz (THz) frequency combs (FCs) with ultra-broad bandwidth of >4 THz and high repetition rate above 20 GHz is presented. An analytical model and diffraction theory demonstrate that the equidistant comb modes are generated from the resonance between the modes of a dielectric waveguide and diffraction waves from a grating adjacent to the waveguide excited by fast electrons. Furthermore, a frequency metrology of the THz FC is developed, and demonstrated to be capable of performing high-precision measurements. This mechanism provides a new way to generate THz FCs with broad bandwidth and large frequency spacing.

12:15 Tu-AM-1-5
Recent Development For THz Vacuum Electronic Devices In IAE
Hongbin Chen; Wenqiang Lei; Guowu Ma; Peng Hu; Yi Jiang; Linlin Hu; Dimin Sun; Yinhu Huang
Institute of Applied Electronics, China Academy of Engineer Physics, China

Institute of Applied Electronics (IAE) of China Academy of Engineer Physics (CAEP) has been developing Grotron and traveling wave tubes operating in the terahertz wave regimes, such as 0.14THz, 0.22THz, 0.34THz. The 0.22THz and 0.34THz pulse folded waveguide TWTs and the CW 0.14THz and 0.22THz folded waveguide TWTs have been measured. By the measurement of 0.22THz pulse TWT, the output power is about 18.2W in 216GHz and 217GHz, the maximum gain is 28.2dB. -3dB bandwidth is about 10GHz at 50% duty cycle. In 0.34THz pulse folded waveguide TWT, the output power is about 1.61W in 338.24GHz, the maximum gain is 23.63dB. -3dB bandwidth is about 1.4GHz at 30% duty cycle. 0.14THz Gyrotron oscillator has been developed and measured at long time pulse work. The output power is about 30kW worked at 60s. 0.67THz and 1THz folded waveguide TWTs is being designed in IAE in this year.

11:00 - 12:30 Tu-AM-2 Supercond. Devices

Chairperson: Masayoshi Tonouchi Petit Amphi

11:00 Tu-AM-2-1
Development Of High-Tc Superconducting THz Emitters
Takanari Kashiwagi¹; Shungo Nakagawa¹; Takayuki Imai¹; Genki Kuwano¹; Youta Kaneko¹; Yukino Ono¹; Shinji Kusunose¹; Takashi Yamamoto²; Hidetoshi Minami¹; Manabu Tsujimoto¹; Kazuo Kadowaki^3
1University of Tsukuba, Japan; ²QuTech, Delft University of Technology, Netherlands; ³Algae Biomass and Energy System R & D Center, University of Tsukuba, Japan

Since the discovery of continuous, coherent THz radiation from intrinsic Josephson junctions (IJJs) constructed in the single crystals of Bi2Sr2CaCu2O8+δ in 2007, various types of device structures have been developed. Thermal management of Joule heat in the IJJ mesa structure is the most important point for the improvement of the radiation characteristics of the IJJ-THz emitters. The radiation frequencies ranging from 0.3 to 2.4 THz, the emission power of ~30 μW and the radiation linewidth of 0.2 GHz at ~0.5 THz were obtained from the thermal managed device structures so far. These characteristics will be discussed in the conference.

11:30 Tu-AM-2-2
Semiconducting Y-Ba-Cu-O Thin Film Detectors At Room Temperature: Front End And Back End Design Issues From Near To Far Infrared
Annick Degardin¹; Vishal Jagtap²; David Alamarguy³; Xavier Galiano²; Alain Kreisler^1
1Sorbonne-University, GeePs, France; ²CentraleSupelec/GeePs, France; ³CNRS/GeePs, France

The Y-Ba-CuO semiconductor material, particularly in its amorphous form (a-YBCO), offers an attractive solution for the easy production of thermal radiation detectors operating at room temperature, because it exhibits a sensitive pyroelectric response. Two aspects must be foreseen, however, for an optimized design of such detectors, in terms of sensitivity and noise level. The front end aspect is related to the optical and thermal coupling of an a-YBCO thin film with the incident radiation. It involves the absorption coefficient, which strongly decreases as wavelength increases. The backend aspect is related to the electrical match between the sensing film and the readout circuitry. It involves the ohmic or Schottky nature of the metal/a-YBCO contacts. We conclude with some design examples and performances, for both planar and trilayer devices. In the near-infrared for instance, noise equivalent power values below 15 pW/√Hz, and detectivity values above 10^9 cm.√Hz/W, could be measured.

11:45 Tu-AM-2-3
Towards Classical Josephson Terahertz Detector
Yuriy Divin; Irina Gundareva; Valery Pavlovskiy
Kotelnikov Institute of Radio Engineering and Electronics, Russian Federation

High-Tc Josephson junctions with Josephson dynamics suppressed by thermal fluctuations were evaluated as detectors of electromagnetic radiation. Classical rectification of THz radiation in the frequency range below 1 THz and in the power range of 4 decades in YBa2Cu3O7-x bicrystal Josephson junctions was experimentally found. As the result of analytical and numerical calculations, the NEP-value of 7x10^(-15) W/Hz^(1/2) and power dynamic range of 3x10^5 at the frequencies up to 1.4 THz were obtained for quasiclassical detection with YBa2Cu3O7-x Josephson junctions operating at the temperature T of 50 K.

12:00 Tu-AM-2-4
Detailed Design Of NbN Based Kinetic Inductance Detectors For Polarimetric Diagnostics
Francesco Mazzocchi¹; Eduard Driessen²; Shibo Shu²; Theo Scherer¹; Dirk Strauss^1
1Karlsruhe Institute Of Technology, Germany; ²IRAM, France

In the following work, we present the detailed design of a polarization sensitive, NbN base Kinetic Inductance Detector to be employed in a low cost, small footprint polarimeter for fusion plasma diagnostics.

12:15 Tu-AM-2-5
Monolithic Terahertz Emitter Of High-temperature Superconductors
Itsuhiro Kakeya¹; Asem Elarabi¹; Keiichiro Maeda¹; Shuma Fujita¹; Manabu Tsujimoto^2
1Kyoto University, Japan; ²University of Tsukuba, Japan

Emission of terahertz electromagnetic (EM) waves from a high critical temperature (Tc) superconductor intrinsic Josephson junction (IJJ) is a new and promising candidate for practical applications of superconducting devices. The emitted EM waves are considered to be coherent because the emission is yielded by synchronization of thousand stacked IJJs consisting of the mesa device. The device has advantages of broad range of frequency tuning and manipulation of polarization with monolithic device structure.

11:00 - 12:30 Tu-AM-3 High Fields 2

Chairperson: Alexander Shkurinov Room 162

11:00 Tu-AM-3-1

Generation Of MV/cm Longitudinal Terahertz Electric Fields From Relativistic Laser-solid Interactions
Abel Hailu Woldegeorgis¹; Takayuki Kurihara²; Mohammed Almassarani¹; Amrutha Gopal^1
1Helmholtz Institute Jena, Helmholtz Institute Jena, Fröbelstieg 3, Germany; ²University of Konstanz, University of Konstanz, Universitatsstr. 10, Germany

We report on the generation and detection of longitudinal terahertz (THz) transient, with field strength of 1.5 MV/cm, at the focus of a radially polarized high-power terahertz beam generated at the rear surface of a thin metal foil irradiated by multi-terawatt laser pulse. An f/1.5 off-axis parabolic mirror was used to focus the collimated THz beam. In addition to the longitudinal field, a transverse field, albeit off-axis, with amplitude in excess of 3 MV/cm was also measured.

11:30 Tu-AM-3-2
Energy Spread And Emittance Control In Segmented High Field Terahertz Driven Electron Accelerators
Dongfang Zhang; Arya Fallahi; Michael Hemmer; Hong Ye; Moein Fakhari; Yi Hua; Huseyin Cankaya; Anne-Laure Calendron; Luis E. Zapata; Nicholas H. Matlis; Franz X. Kärtner
Deutsches Elektronen-Synchrotron (DESY), Germany

Here we use a two-stage segmented-terahertz-electron-accelerator-and-manipulator (STEAM) setup to demonstrate control over the electron beam energy, energy spread and emittance. The first rebunching stage is used to tune the duration of 55 keV electron bunches that enables femtosecond phase control at the second accelerating stage. For optimized parameters, energy spread and emittance are reduced by 4x and 6x, respectively, relative to operation with the first stage off. A record energy gain of ~70 keV was achieved at a peak accelerating field of 200 MV/m, resulting in >100% energy boost in a THz-powered accelerator for the first time.

11:45 Tu-AM-3-3
High Harmonic Generation In Metallic Phase Of 2H-NbSe_2
Kousei Shimomua; Kento Uchida; Kohei Nagai; Satoshi Kusaba; Koichiro Tanaka
Department of Physics, Graduate School of Science, Kyoto University, Japan

High harmonics up to the 9th order have been confirmed in metallic phase of 2H-NbSe2 with intense mid-infrared light. They show the nonperturvative excitation power dependence, and their efficiency are almost independent of the polarization direction to the crystal axis. Our Numerical calculation based on the intraband current model reproduces the experimental results, suggesting that the carrier distribution in k-space plays a crucial role for the high harmonics in metal.

12:00 Tu-AM-3-4
Terahertz Generation By Kerr Effect At Metal Surfaces
Bastien Muller; Maxime Bernier; Emilie Herault; Jean-Louis Coutaz
IMEP-LAHC, France

The emission of terahertz radiation from laser-excited thick metal samples through Kerr effect has been detected for the first time to the authors' knowledge. The observed THz waveforms are generated through nonlinear electronic processes at surfaces (optical rectification) and in the bulk (Kerr effect) of gold samples.

12:15 Tu-AM-3-5

Extremely High Field Single-cycle Terahertz Pulse Sources Based On Echelon Structures
György Tóth¹; László Pálfalvi¹; József András Fülöp²; Gergő Krizsán¹; Priyo S. Nugraha³; Zoltán Tibai¹; Levente Tokodi¹; Gábor Almási¹; János Hebling^1
1University of Pécs, Hungary; ²MTA-PTE High Field Research Group, Hungary; ³Szentágothai Research Centre, Hungary

Three different echelon based structures for the generation of intense THz pulses were suggested and simulated. Their advantages are the energy scalability and the symmetric THz beam profile. Focused single cycle THz pulses up to ~50 MV/cm peak electric field level are predicted with these sources. Such sources can basically promote the realization of THz driven electron and proton accelerators.

11:00 - 12:30 Tu-AM-4 Telecom 1

Chairperson: Tadao Nagatsuma Room 269

11:00 Tu-AM-4-1

Simulation And Automatic Planning Of 300 GHz Backhaul Links
Bo Kum Jung; Nils Dreyer; Johannes Eckhardt; Thomas Kürner
TU Braunschweig, Germany

The IEEE Standard 802.15.3d defines a communication systems allowing wireless solutions for backhaul links operating at 300 GHz with data rates of 100 Gbit/s and beyond. The European Horizon 2020 ThoR project works towards the demonstration of such a solution. One of the goals of ThoR is to develop algorithms for automatic planning of 300 GHz backhaul links and the derivation of planning guidelines. In this paper, an automatic algorithm for the planning of 300 GHz backhaul links using 3D ray tracing taking into account atmospheric effects is presented. The influence of both the applied antennas and the weather conditions are evaluated for an automatically planned network by using a realistic scenario of an ultra-dense network in the city of Hannover.

11:30 Tu-AM-4-2
Bidirectional K-Band Photonic/Wireless Link For 5G Communications
Alvaro Morales; Dimitrios Konstantinou; Simon Rommel; Thiago Roberto Raddo; Ulf Johannsen; Chigo Okonkwo; Idelfonso Tafur Monroy
Eindhoven University of Technology, Netherlands

A bidirectional analogue radio-over-fiber link based on photonic heterodyning and time-division duplex is experimentally demonstrated, successfully transmitting 5G OFDM signals with data rates of 2.4 Gbit/s and 1.2 Gbit/s in down- and uplink directions over 4 m of wireless distance.

11:45 Tu-AM-4-3
Scattering Analysis Of Terahertz Wireless Links By Rough Surfaces
Jianjun Ma¹; Rabi Shrestha²; Wei Zhang²; Lothar Moeller³; Daniel Mittleman^2
1Beijing Institute of Technology, China; ²Brown University, United States; ³New Jersey Institute of Technology, United States

This work presents the diffuse bistatic scattering response of metallic rough surfaces using a data stream at THz frequency range. NLOS links can be established by the form of diffuse scattering rays when a LOS and specular NLOS links are blocked. So non-specular NLOS paths can play a valuable role in future THz wireless systems with a highly directional beam.

12:00 Tu-AM-4-4
Direct Terahertz Communications With Wireless And Fiber Links
Xiongbin Yu¹; Tomoyuki Miyamoto²; Katsunori Obata²; Yasuo Hosoda²; Jae-Young Kim³; Masayuki Fujita¹; Tadao Nagatsuma^1
1Osaka University, Japan; ²Pioneer Corporation, Japan; ³ROHM Co., Ltd, Japan

We have successfully demonstrated a direct THz communications link that employs both a wireless and a fiber portion, for advanced communication systems. Currently, the greatest obstacle is the efficiency of overall link, which we intend to overcome by refining the connection between the photonic-crystal waveguide and THz fiber, in order to achieve a higher data rate. We also aim to employ RTDs as both transmitter and receiver, in order to realize an all-electronic system that does not require laser excitation. Such THz systems may find uses not only in communications, but also in such as remoting sensing, security and medical applications.

12:15 Tu-AM-4-5
Towards Super-heterodyne THz Links Pumped By Photonic Local Oscillators
Iulia Dan¹; Shintaro Hisatake²; Pascal Szriftgiser³; Ralf-Peter Braun⁴; Ingmar Kalfass¹; Guillaume Ducournau^5
1Institute of Robust Power Semiconductor Systems, Univ Stuttgart, Germany; ²Gifu Univ, Japan; ³PhLAM, France; ⁴DEUTSCHE TELEKOM AG, Germany; ⁵IEMN CNRS/Université de Lille, France

We present in this paper wireless data transmission experiments in a superheterodyne wireless system based on millimeterwave monolithic integrated circuits at a center frequency of 300 GHz, driven by photonic local oscillator (LO). Superheterodyne operation is attractive for compliance with the recent IEEE802.15.3d frequency standard. The super-heterodyne transmission with two channels is realized using an AWG and a photonic-based LO. The paper presents initial transmission experiments realized using two channels in the 300 GHz band

11:00 - 12:30 Tu-AM-5 QW

Chairperson: Yanko Todorov Room 101

11:00 Tu-AM-5-1

Quantum Well Infrared Detectors In The Strong Light-matter Coupling Regime
PB Vigneron¹; S Pirotta¹; I Carusotto²; NL Tran¹; G Biasiol³; JM Manceau⁴; A Bousseksou⁴; Raffaele Colombelli^4
1Centre de Nanosciences et Nanotechnologies (C2N), France; ²University of TRENTO, BEC Center, Italy; ³TASC Laboratory, Italy; ⁴Centre de Nanosciences et Nanotechnologies, France

We report quantum well mid-infrared photo-detectors operating in the strong light-matter coupling regime. It is an ideal system to elucidate the elusive problem of the injection of electrons (single-particles) into polaritonic modes (bosonic excitations). We have obtained experimental information on the transfer function between a polaritonic system and an electronic reservoir. This approach opens promising avenues in view of adding previously unavailable functionalities to quantum well detectors and improving their performance.

11:30 Tu-AM-5-2
High Speed Quantum Well Infrared Heterodyne Receivers At 4.9µm
Gregoire Vallet¹; Djamal Gacemi¹; Azzurra Bigioli¹; Angela Vasanelli¹; Yanko Todorov¹; Carlo Sirtori¹; Etienne Rodriguez^2
1Laboratoire de Physique de l'Ecole Normale Superieure, CNRS, France; ²CINTRA CNRS/NTU/THALES, Singapore

We have realized high-speed quantum well infrared photodetectors (QWIPs) for the detection of coherent radiation at 4.9 Ãfâ?sÃ,µm wavelength. Our devices have a detectivity of 4 x 10-10 cm Hz1/2 W-1 at 77 K and a flat response up to 30 GHz.

11:45 Tu-AM-5-3
Far And Mid IR Stimulated Emission In HgCdTe QW Heterostructures
Vladimir Gavrilenko¹; Sergey Morozov¹; Vladimir Rumyantsev¹; Mikhail Fadeev¹; Vladimir Utochkin¹; Nikita Kulikov¹; Alexandre Dubinov¹; Vladimir Aleshkin¹; Nikolay Mikhailov²; Sergey Dvoretskii²; Frederic Teppe³; Carlo Sirtori^4
1Institute for Physics of Microstructures, Russian Federation; ²A.V.Rzhanov Institute of Semiconductor Physics, Russian Federation; ³Laboratoire Charles Coulomb, CNRS & Universite Montpellier, France; ⁴Laboratoire de Physique de l'Ecole Normale Superieure, France

Stimulated emission (SE) at wavelengths up to 24 μm (12.5 THz) and down to 2.8 μm is demonstrated from HgCdTe quantum well (QW) heterostructures. Non-radiative Auger recombination is show to be mitigated due to relativistic energy spectrum. Pump-probe carrier lifetime measurements show that further increase in SE wavelength is feasible up to 60 μm (5 THz). In the short wavelength range SE down to 2.8 μm is demonstrated at temperatures available with Peltier coolers.

12:00 Tu-AM-5-4
Room Temperature THz Intersubband Transitions In Continuously-graded AlxGa1-xAs Parabolic Quantum Wells
Christopher Deimert¹; Paul Goulain²; Jean-Michel Manceau²; Adel Bousseksou²; Raffaele Colombelli²; Zbig Wasilewski^1
1University of Waterloo, Canada; ²centre de nanosciences et naotechnologies, France

We demonstrate room temperature intersubband transitions in the THz range using continuously-graded AlxGa1 xAs parabolic quantum wells. Below 100K, the linewidth of the transition reaches a record-low value of 5.7% of the central frequency.

12:15 Tu-AM-5-5
High Sensitivity 9?m Metamaterial Infrared QC Detectors At 300K
Azzurra Bigioli¹; Giovanni Armaroli¹; Daniele Palaferri²; Yanko Todorov¹; Angela Vasanelli¹; Djamal Gacemi¹; Li Lianhe³; Giles Davies³; Edmund Linfield³; Carlo Sirtori^1
1Laboratoire de Physique de l'Ecole Normale Superieure, France; ²Laboratoire Matériaux et Phénomènes Quantiques, France; ³School of Electronic and Electrical Engineering, Leeds, United Kingdom

Quantum Cascade Detectors are promising devices for high-temperature mid-infrared detection. The responsivity, related to its photovoltaic working principle, still suffers from lower responsivity respect to a photoconductive device such as QWIP. Here, we demonstrate that inserting a QCD detector in a photonic metamaterial made of patch-antenna microcavities, we can boost light-matter interaction reaching responsivity value in the order of 50mA/W at room temperature, the highest value reported in the literature

11:00 - 12:30 Tu-AM-6 Metamaterials 1

Chairperson: Michele Ortolani Room 151

11:00 Tu-AM-6-1

Broadband Achromatic Metalens In Terahertz Regime
Yiming Zhu; Qingqing Cheng; Lin Chen; Yan Peng
University of Shanghai for Science & Technology, China

We demonstrate the achromatic metalens with C-shape units working from 0.3 to 0.8 THz with a bandwidth of approximately 91% over the center wavelength. The achromatic focusing has been observed both experimentally and numerically, with the size of focal spot closed to ?. Meanwhile, the designed metalens possesses high working efficiency of more than 68% at the peak and a relatively high numerical aperture (NA) of NA=0.385 in order to obtain high spatial resolution. We further show the robustness of our C-shape structures, considering lateral shape deformations and deviations of etching depth. Our work successfully demonstrates the THz achromatic metalens, which opens an avenue for the future applications of terahertz meta-devices on spectroscopy, time-of-flight tomography and hyperspectral imaging system.

11:30 Tu-AM-6-2
Terahertz 3D Components Made From Metamaterials
Haruaki Nakao; Takehito Suzuki
Tokyo University of Agriculture and Technology, Japan

A realization of next-generation ultrafast wireless communication (6G) and security imaging in the terahertz waveband is a question of time because of the rapid development of terahertz oscillators. However, terahertz components have yet to be developed whereas components in the optical region and millimeter waveband provide sufficient support for technological and scientific progress. Here we produce a reflectionless metamaterial with an extremely high refractive index of 12.3 in the 0.3-THz band and apply it to a 3D phase delay component for high-performance gradient-index terahertz lenses. We also demonstrate a large-aperture robust polarizer with an extreme sensitivity of high extinction ratios below -50 dB consisting of a metamaterial with a large negative relative permittivity of -97.6. The 3D terahertz components utilizing unprecedented materials would contribute to the development of a future industry based on terahertz applications.

11:45 Tu-AM-6-3
Realizing Sub-diffraction Focusing For Terahertz
Ayato Iba¹; Calvin W. Domier²; Makoto Ikeda¹; Atsushi Mase³; Anh-Vu Pham²; Neville C. Luhmann, Jr^2
1Sensing Technology Department, Asahi-Kasei Corporation, Japan; ²Department of Electrical and Computer Engineering, University of California, Davis, United States; ³Global Innovation Center, Kyushu University, Kasuga-koen, Japan

Measurement resolution is one of the most important elements for industrial applications. However, conventional lenses for terahertz (THz) or millimeter-wave cannot achieve high resolution due to the diffraction limit. Here, we demonstrate that two types of super-oscillatory lenses are very effective for subdiffraction focusing at THz.

12:00 Tu-AM-6-4
All-dielectric Guided-mode Resonance Filters In THz Region
Hyeon Sang Bark¹; In Hyung Baek¹; Kyu-Ha Jang¹; young Uk Jeong¹; Tea-In Jeon^2
1Korea Atomic Energy Research Institute, Republic of Korea; ²Korea Maritime and Ocean University, Republic of Korea

In summary, because the proposed GMR filters have a high Q-factor, tunable filter and good polarizer characteristics, it has potential for THz applications in modulator, band pass filter, reflector, sensor [3] and bio-medical technologies in the future.

12:15 Tu-AM-6-5
Extraordinary THz Absorption In 2D Material-dielectric Integrated Metasurfaces
Sara Arezoomandan; Hugo Condori Quispe; Berardi Sensale-Rodriguez
University of Utah, United States

This work discusses our recent findings on 2D material-dielectric integrated metasurfaces, as an alternative approach to 2D material-metal hybrid metamaterials, for providing efficient control of the electromagnetic beam propagation at THz wavelengths. The analyzed structures consist of a passive dielectric pattern and a reconfigurable 2D material sheet whose THz optical conductivity can be actively tuned. We show that via optimizing the geometric dimensions in the patterns it is possible to attain almost complete absorption by the 2D material at an arbitrary frequency of interest.

11:00 - 12:30 Tu-AM-7 Gas Spectro. & Sensing 2

Chairperson: Gaël Mouret Room 201

11:00 Tu-AM-7-1

High-resolution Fast Terahertz Time-domain Gas Spectroscopy Based On A Fine Comb Spectral Structure Of The NovoFEL
Vitaly Kubarev¹; Yaroslav Getmanov¹; Evgeny Chesnokov²; Pavel Koshlyakov^2
1Budker Institute of Nuclear Physics, Russian Federation; ²Institute of Chemical Kinetics and Combustion, Russian Federation

High coherency and monochromaticity of the terahertz Novosibirsk Free-Electron Laser (NovoFEL) is appeared in very narrow comp spectral structure of its radiation (relative line's width is 2E-8, interval between lines is 5.6 MHz, total width of the comb-structure is 6-12 GHz). Sampling time-domain spectroscopy with resolution of order of the line width (~ 100 kHz) needs measuring time about of 20 µsec per one sampling point and only 56 slow sampling points to overlap the full NovoFEL comb spectrum. Shift of the comb structure will be made by changing of length of the NovoFEL optical resonator. Universal terahertz gas laser (line width ≤0.5E-8) will be used as local oscillator in the heterodyne spectrometer.

11:30 Tu-AM-7-2
Free Induction Decay Signals Stimulated By Photomixing
Fuanki Bavedila¹; Guillaume Ducournau¹; Jean-François Lampin¹; Emilien Peytavit¹; Arnaud Cuisset²; Gaël Mouret²; Cedric Bray³; Robin Bocquet²; Francis Hindle^2
1IEMN CNRS/Université de Lille, France; ²Laboratoire de Physico-chimie de l'Atmosphère ULCO, France; ³Institut des Sciences Moléculaires Université de Bordeaux, France

An optically driven photoconductor device is electrically pulsed to provide a powerful pulse around 206 GHz. The pulsed radiation polarizes the OCS gas which emits a free induction decay signal that is observed after the end of the pulse. This is the first step in the development of a photonic chirped pulsed spectrometer.

11:45 Tu-AM-7-3
Terahertz Differential Absorption Spectroscopy Using Multi-Furcated Nd:YAG Microchip Laser For Gas Sensing
Yuma Takida¹; Toshiyuki Ikeo²; Kouji Nawata¹; Yoshio Wada²; Yasuhiro Higashi²; Hiroaki Minamide^1
1RIKEN, Japan; ²Ricoh Company, Ltd., Japan

We demonstrate a frequency-domain differential absorption spectroscopy in the terahertz (THz) range for gas sensing applications. Our system is based on an injection-seeded THz-wave parametric generator driven by a multi-furcated Nd:YAG microchip laser. Within a single excitation cycle of the laser, the is-TPG generates up to three narrowband THz-wave pulses that are separated in time by 80 µs and in frequency by 11 GHz, which is due to the spatial hole burning effect in the laser cavity. These pulses can be directly used to measure differential absorption signals, and first and second derivative spectra of target gas molecules without measuring reference spectra.

12:00 Tu-AM-7-4
Determining DHO Detection Limits For A Frequency Domain THz Spectrometer Coupled To A Light-weight Multi-pass Sample Cell
Joseph Demers; Elijah Dale
Bakman Technologies, United States

A fringe-free, frequency domain terahertz spectrometer connected to a custom fabricated, light-weight multi-meter multi-pass sample cell was employed to measure the 1.492 THz, 1.507 THz and 1.523 THz molecular transitions of DHO over various pressures. We will report on the detectable concentrations of the DHO achieved with the portable instrument.

12:15 Tu-AM-7-5
THz/Far-IR Astrophysical Studies At The Australian Synchrotron
Dom Appadoo
ANSTO/Australian Synchrotron, Australia

THz synchrotron spectroscopy has become an important tool in the identification and quantification of molecular species of astrophysical interest; it is a routinely used technique as it is well established that synchrotron radiation offers a S/N advantage over conventional thermal sources. The brightness advantage is perfectly suited for high-resolution gas-phase spectroscopy, and at the Australian Synchrotron, this advantage is limited to energies lying below 1500 cm-1; however, a flux advantage is maintained for energies lying only below 350 cm-1 which facilitates the study of homogeneous condensed-phase samples. The THz/Far-IR beamline is equipped with a suite of both gas-phase and condensed-phase techniques to enable research on interstellar molecular species, and in this paper, the beamline capabilities available for the study of molecular species of astrophysical interest will be presented.

12:30-14:00 - Lunch

14:00-16:00 Parallel sessions Tu-PM1

14:00 - 16:00 Tu-PM1-1 Gyrotron 5

Chairperson: Alexander Litvak Amphi Lavoisier

14:00 Tu-PM1-1-1
Characterizing The Accelerating Mode Of A Dielectric-lined Waveguide Designed For Terahertz-driven Manipulation Of Relativistic Electron Beams
Vasileios Georgiadis¹; Morgan Hibberd¹; Alisa Healy²; Daniel Lake²; Graeme Burt²; Steven Jamison²; Darren Graham^1
1The University of Manchester, The University of Manchester, Oxford Road, United Kingdom; ²University of Lancaster, University of Lancaster, Bailrigg, United Kingdom

We report on the generation of a terahertz beam with a quasi-TEM01 mode by exploiting the interferometric recombination of two linearly polarized emitters in a combined spintronic source. The generated THz beam was used to characterize the accelerating mode of a dielectric-lined waveguide (DLW) to inform on the recent demonstration of relativistic electron beam manipulation achieved with this THz-driven DLW at the CLARA research facility at Daresbury Laboratory.

14:30 Tu-PM1-1-2
First Operation Of Ka-band High-current Relativistic Gyrotron
Alexander Leontyev¹; Edward Abubakirov¹; Andrej Denisenko¹; Alexey Fedotov¹; Roman Rozental¹; Vladimir Tarakanov^2
1Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation; ²Moscow Engineering Physics Institute, Russian Federation

The results of the first operation of a pulse Ka-band gyrotron with output radiation power more than 110 MW are presented. The gyrotron was excited by electron beam with a current of up to 2 kA and particle energy of up to 500 keV, formed by an explosive emission cathode with subsequent transverse velocities pumping in a non-uniform field produced by a short coil (kicker) to a state with a pitch-ratio of about 1.

14:45 Tu-PM1-1-3
An Experimental Investigation Of A 0.8 THz Gyrotron With An Improved Mode Selection
Mikhail Glyavin¹; Toshitaka Idehara²; Eduard Khutoryan³; Svilen Sabchevski⁴; et al^1
1Institute of Applied Physics RAS, Russian Federation; ²FIR UF, Japan; ³IRE NASU, Ukraine; ⁴IE BAS, Bulgaria

In this paper, we present and discuss the latest experimental results from the investigation of the operational performance of a 0.8 THz double-beam gyrotron, which has been developed and manufactured recently in the framework of an international research project led by IAP-RAS and FIR UF. After the initial tests, the current experiments have been focused not only on the study of the operation at the design mode TE8,5 (at the second harmonic of the cyclotron frequency) but also of several other modes the generated radiation of which could be appropriate for various other applications besides the envisaged 1.2 GHz DNP-NMR spectroscopy. The obtained results give a deeper insight into the specifics of the operation of the double-beam gyrotron and especially on its capability to provide an improved mode selection and therefore a single mode second harmonic operation.

15:00 Tu-PM1-1-4
Observation Of Multi-Peak Frequency Spectrum In A High Power Sub-THz Gyrotron
Teruo Saito¹; Shunsuke Tanaka¹; Ryuji Shinbayashi¹; Yuusuke Yamaguchi¹; Masafumi Fukunari¹; Yoshinori Tatematsu¹; Maria Melnikova²; Nikita Ryskin^2
1University of Fukui, Japan; ²Saratov State University, Russian Federation

Equi-distantly distributed multi-peak frequency spectrum was observed in a high power 300 GHz band gyrotron for the case of strong reflection off the vacuum window. An oscillation mode different from the design mode can oscillate by adjusting the magnetic field in the cavity. However, a large fraction of the output wave is reflected by the vacuum window. A theoretical calculation shows that the multi-peak frequency spectrum stems from periodic amplitude variation that is caused by mode competition between the oscillating co-rotating mode and the counter-rotating mode originating from the reflected wave.

15:15 Tu-PM1-1-5
Demonstration Of A High Power Frequency-Tunable 0.22-THz Gyrotron Operating In High-Order Axial Modes
Xiaotong Guan; Wenjie Fu; Dun Lu; Tongbin Yang; Xuesong Yuan; Yang Yan
University of Electronic Science and Technology, China

To explore the approach for generating high power frequency-tunable sub-THz to THz radiation, a 0.22-THz high-order axial modes (HOAMs) gyrotron is developed and tested in TRC-UESTC. The proof-of-principle experimental results demonstrate that a series of HOAMs in a long gyrotron cavity are excited successfully by an electron beam of high voltage and high current. A frequency tuning range of 0.79 GHz around 219 GHz has been achieved by tuning the operating magnetic field and operating in the first four axial modes. And during the frequency tuning, the out power kept no less than 0.45 kW, while the maximum output power was 3.80 kW. These experimental results of axial mode transition in high power sub-terahertz gyrotron should be conductive to the future development of frequency-tunable gyrotron towards some up-and-coming novel terahertz applications.

15:30 Tu-PM1-1-6
95 GHz Gyrotron With Water Cooled Magnet And High Average Power
Moritz Pilossof
Ariel University, Israel

Abstract-- A 95 GHz gyrotron with water cooled copper magnet delivering high average power was assembled. The cavity interaction mode is TE02 at the second cyclotron harmonic. Internal mode converter is used to convert the interaction mode to quasi-Gaussian mode at the gyrotron output window. A ~1.8T magnetic field is produced by water cooled copper electro-magnet. The magnet and the gyrotron have immediate turn on and off time when the cathode is worm (<1s). Initial results will be presented.

15:45 Tu-PM1-1-7
Multibeam And Multibarrel Gyrotrons
Vladimir Zapevalov; Vladimir Zapevalov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

The report analyzes the perspective of multibeam and multibarrel version of gyrotron for possibility of frequency tuning and improved mode selection at gyrotron working on the gyrofrequency harmonics.

14:00 - 16:00 Tu-PM1-2 Solid State 4

Chairperson: Dmitry Khokhlov Petit Amphi

14:00 Tu-PM1-2-1

Infrared/Terahertz Photogalvanic Spectroscopy Of Three And Two Dimensional Topological Insulators
Sergey Ganichev
Terahertz Center, University of Regensburg, Germany

The paper overviews experimental and theoretical studies of photogalvanic and photon drag effects induced in various in three-dimensional (3D) and 2D topological insulators (TI) by polarized infrared/terahertz (IR/THz) radiation. e present the state-of-the-art of this subject, including both recent advances and well-established results. Various physical mechanisms of photogalvanic and photon drag effects in TI systems are described including experimental achievements, phenomenological description, models visualizing physics of nonlinear responses, and microscopic theory of individual effects. Several examples for the characteristics determined by applying photocurrents are: the Fermi velocity, the cyclotron masses as a function of carrier density and temperature, the orientation of surface domains in 3D TIs, and the surface state mobility.

14:30 Tu-PM1-2-2
Terahertz Electron Paramagnetic Resonance Spectroscopy using An Ultrathin Membrane Device
Eiji Ohmichi; Hideyuki Takahashi; Tsubasa Okamoto; Daiki Hachiya; Hitoshi Ohta
Kobe University, Japan

A novel terahertz (THz) electron paramagnetic resonance (EPR) spectroscopy technique is presented. The use of an ultrathin membrane device allows sensitive EPR detection of small volume samples in the frequency region up to 0.65 THz. We show THz EPR spectroscopy results on microliter solution of myoglobin and a tiny single crystal of a magnetically ordered sample.

14:45 Tu-PM1-2-3
Influence Of Cu-doping On Terahertz Conductivity And Temperature-driven Phase Transition In NdNiO3 Thin Films
Mahesh Chandra¹; V. Eswara Phanindra²; S. Prabhu³; Krushna Mavani^1
1Indian Institute of Technology Indore, India; ²Indian Institute of Science Education and Research Bhopal, India; ³Tata Institute of Fundamental Research, India

Perovskite nickelates show the first order metal-insulator transition. Doping of 3d metal ions at Ni-site can drastically change the electronic properties. We have deposited and studied Cu-doped NdNiO3 thin films for structural and electronic properties. Merely 2% Cu-dopingat Ni-site induces a metallic state in otherwise insulating NdNiO3 film at low temperatures. The terahertz conductivity shows Drude behavior and the conductivity is tuned by Cu-doping in these films.

15:00 Tu-PM1-2-4
Calculating The Complex Permittivity Of Powdered Crystalline Materials
Andrew Burnett; Calum Towler; John Kendrick
School of Chemistry, University of Leeds, United Kingdom

Solid-state density functional theory calculations including periodic boundary conditions have become well established for calculating the THz spectra of crystalline materials. Here we compare a range of DFT programs and calculation parameters including a number of van der Waals' dispersive corrections in combination with our post-processing tool, PDielec, to calculate the complex permittivity of a range of powdered crystalline materials.

15:15 Tu-PM1-2-5
Spin And Lattice Dynamics Of Multiferroic SrMn7O12 Studied By THz And Infrared Spectroscopies At Low Temperatures And In Magnetic Field
Filip Kadlec¹; Veronica Goian¹; Dmitry Nuzhnyy¹; Christelle Kadlec¹; Jakub Vít¹; Fedir Borodavka¹; Iana S. Glazkova²; Alexei A. Belik³; Stanislav Kamba^1
1Institute of Physics CAS, Czech Republic; ²Lomonosov Moscow State University, Russian Federation; ³National Institute for Materials Science, Japan

Multiferroic SrMn7O12 crystals are isostructural with CaMn7O12 which is known for its unusual symmetry properties and a record-high spin-induced polarization. We studied SrMn7O12 ceramics by THz time-domain and Fourier-transform infrared spectroscopies upon varying temperature and magnetic field. In the magnetic phases, we observed spin waves gaining strength from phonons; thus, they are assigned to electromagnons. We discuss the observed persistence of several low-temperature vibrational modes above the high-temperature phase transition, and the impact of atomic substitution with regard to CaMn7O12.

15:30 Tu-PM1-2-6
Identification And Characterization Of 'Killer-Modes' In Organic Semiconductors With Terahertz Spectroscopy
Peter Banks; Michael Ruggiero
The University of Vermont, United States

Organic semiconductors are promising modern optoelectric materials, with countless potential applications ranging from flexible displays to photovoltaics. The applicability of these materials is largely driven by their charge carrier mobility, which is strongly influenced by low-frequency vibrations. In this work, the specific low-frequency vibrations that exhibit strong electron-phonon coupling, deemed 'killer-modes', in organic semiconductors are determined using a combination of terahertz time-domain spectroscopy and solid-state density functional theory. The results of this study enable a concerted synthetic effort to rationally design novel materials, utilizing intermolecular forces to stiffen lattice dynamics, to ultimately improve charge carrier mobility.

15:45 Tu-PM1-2-7
Effects Of Low Content Enantiomer Impurity In L-histidine Crystal Observed By Terahertz Spectroscopy
Tetsuo Sasaki¹; Tomoaki Sakamoto²; Makoto Otsuka^3
1Shizuoka University, Japan; ²National Institute of Health Sciences, Japan; ³Musashino University, Japan

Effects of enantiomer impurity molecule at low content on THz spectrum were studied. L-histidine crystal was grown controlled to monoclinic form B from ethanol-rich solvent. D-histidine was added in the range 0.05 to 10.0 % in the solvent before recrystallization. Peak frequency shifts of absorption lines of L-histidine at 10 K on the relation with D-histidine content were evaluated by high frequency accurate THz spectrometer. It was shown that high sensitive detection of enantiomer impurity was possible until DL racemic compound crystal was formed with increasing D-histidine content.

14:00 - 16:00 Tu-PM1-3 THz Devices 1

Chairperson: Stefano Barbieri Room 162

14:00 Tu-PM1-3-1

Free-space Coupling Of Terahertz Whispering-gallery Modes
Dominik Vogt; Angus Jones; Rainer Leonhardt
University of Auckland, New Zealand

We report on free-space coupling of high quality (Q) spherical THz whispering-gallery mode resonators (WGMRs) as a simple alternative to more complex waveguide and prism coupling. Excitation efficiencies up to 50% to WGMs with Q-factors of 1.5x10^4 at 0.7THz are achieved.

14:30 Tu-PM1-3-2
Terahertz Polarization Splitter Based On Parallel-plate Waveguide Technology
Arturo Hernandez-Serrano; Emma Pickwell-MacPherson
University of Warwick, United Kingdom

In this work we present a terahertz polarization splitter based on a parallel-plate waveguide (PPWG). The proposed structure consists of a stacked array of stainless steel plates with 0.8mm spacing. The device is capable of splitting the two orthogonal polarization components (TM and TE) in a frequency range of 250GHz to 500GHz.

14:45 Tu-PM1-3-3
High-Performance Frequency Selective Surface Filters For Terahertz Applications
Sergei Kuznetsov¹; Nazar Nikolaev²; Andrey Arzhannikov^3
1Rzhanov Institute of Semiconductor Physics SB RAS, Russian Federation; ²Institute of Automation and Electrometry SB RAS, Russian Federation; ³Budker Institute of Nuclear Physics SB RAS, Russian Federation

We review the results of extensive R&D activity focused on elaborating high-performance quasi-optical filters using the technology of frequency selective surfaces. The band-pass, low-pass, and high-pass devices operating at subterahertz and terahertz frequencies are described. The issues of design optimization, lithographic fabrication, and spectral characterization of the developed filters alongside with their practical applications are considered.

15:00 Tu-PM1-3-4
Giant Dual-mode Graphene-based THz Modulator
Liang-Hui Du¹; Pei-Ren Tang²; Jiang Li¹; Li-Guo Zhu^1
1Institute of Fluid Physics, China Academy of Engineering Physics, China; ²University of Science and Technology of China, China

We report a high-performance terahertz (THz) modulator with dual-operation mode. For the pulse operation mode, the proposed THz modulator has the advantage of high modulation depth (MD) and can operate in a broadband frequency range. We have experimentally achieved a MD larger than 90% for the fifth-order pulse THz echo at 0.8 THz and the MD stays larger than 75% in a broadband frequency range larger than 1 THz. While, for the coherent operation mode, the Fabry-Perot (F-P) interference effect has been taken into consideration and a MD larger than 75% at 0.76 THz has also been realized.

15:15 Tu-PM1-3-5
Photonic Bandgap Bragg Waveguide-based Terahertz Microfluidic Sensor
Yang Cao; Kathirvel Nallappan; Hichem Guerboukha; Thomas Gervais; Maksim Skorobogatiy
Polytechnique Montreal, Canada

A 3D printed photonic bandgap Bragg waveguide-based resonant microfluidic sensor operating in the THz spectral range is theoretical analyzed and experimental studied. The analytes are injected into a microfluidic channel to a defect layer region which results in a modal anti-crossing phenomenon. By tracking the spectral positions of the induced absorption dips and phase changes of the transmission spectra of various liquids, we measure a sensitivity of 110 GHz/RIU. The proposed sensor features high reliability and can provide a non-contact measurement method for real-time monitoring of the refractive index change of liquid flow in practical applications.

15:30 Tu-PM1-3-6

Efficient Ultrafast THz Modulators Based On Negative Photoconductivity In Controllably Doped Carbon Nanotubes

Burdanova, Maria¹; Tsapenko, Alexey²; Satco, Daria²; Kashtiban, Reza¹; Mosley, Connor³; Monti, Maurizio¹; Staniforth, Michael¹; Sloan, Jeremy¹; Gladush, Yuriy²; Nasibulin, Albert²; Lloyd-Hughes, James^1
1The University of Warwick, United Kingdom ; ²Skolkovo Institute of Science and Technology, Russian Federation

Large diameter single-walled carbon nanotubes films are shown to have a doping level and THz conductivity that can be readily controlled using adsorption doping or electrostatic gating. The giant negative photoconductivity observed upon optical excitation is due to a rapid reduction in mobile carrier density, synchronously to a lowering of the momentum scattering rate. The large modulation depth and tunable recovery time open prospects for carbon nanotube films in ultrafast and THz devices.

15:45 Tu-PM1-3-7
Engineered Silicon For Efficient Mm-Wave And THz Modulators
Lauren Barr¹; Ian Hooper¹; Nicholas Grant²; Samuel Hornett¹; Christopher Lawrence³; John Murphy²; Euan Hendry^1
1University of Exeter, United Kingdom; ²University of Warwick, United Kingdom; ³QinetiQ, United Kingdom

Large diameter single-walled carbon nanotubes films are shown to have a doping level and THz conductivity that can be readily controlled using adsorption doping or electrostatic gating. The giant negative photoconductivity observed upon optical excitation is due to a rapid reduction in mobile carrier density, synchronously to a lowering of the momentum scattering rate. The large modulation depth and tunable recovery time open prospects for carbon nanotube films in ultrafast and THz devices

14:00 - 16:00 Tu-PM1-4 Telecom 2

Chairperson: Guillaume Ducournau Room 269

14:00 Tu-PM1-4-1

12.5-Gbit/s Wireless Link At 720 GHz Based On Photonics
Tadao Nagatsuma¹; Masato Sonoda¹; Taiki Higashimoto¹; Li Yi¹; Jeffrey Hesler^2
1Osaka University, Japan; ²Virginia Diodes, Inc., United States

This paper addresses a development of 600-GHz band wireless links based on photonics technologies. An error-free transmission at a bit rate of >12.5 Gbit/s has been demonstrated for the first time at 720 GHz using a photodiode-based transmitter and a Schottky-barrier-diode mixer receiver.

14:30 Tu-PM1-4-2
The Influence Of RF Front-End Imperfections On Performance Of A 220- 260 GHz Tunable M-QAM Wireless Link In SiGe HBT Technology
Janusz Grzyb¹; Pedro Rodriguez Vazquez¹; Bernd Heinemann²; Ullrich Pfeiffer^1
1University of Wuppertal, Germany; ²IHP- Leibniz-Institut für Innovative Mikroelektronik, Germany

This paper presents system-level characterization and performance evaluation for higher-order M-QAM modulation formats of a fully-electronic 1-m wireless link with two highly-integrated direct-conversion quadrature TX and RX modules in 0.13-υm SiGe HBT technology operating with a tunable 220-260 GHz LO carrier. With the limited baseband bandwidth of 15 GHz, the maximum achieved data rates for 16-/32-/64-QAM modulation are 90 Gbps (EVM of 14.6%), 90 Gbps (EVM of 11.9%) and 81 Gbps (EVM of 8.7%), respectively.

14:45 Tu-PM1-4-3
A Metal Wire Waveguide For Terabit DSL
Rabi Shrestha¹; Kenneth Kerpez²; Chan Soo Hwang²; Mehdi Mohseni²; John Cioffi²; Daniel M. Mittleman^1
1Brown University, United States; ²ASSIA, Inc., United States

We investigate the propagation of terahertz radiation on a complex multi-element metal wire waveguide ensheathed in a metal jacket. Mode mixing due to bends and nonuniformities along the waveguide axis result in a nearly random mode pattern at the output. This stochastic mixing is ideal for a vectored transmission, analogous to the multiple-input, multiple-output (MIMO) concept commonly used in wireless networking and could enable terabit-per-second data rates on the existing cables already in use by DSL systems.

15:00 Tu-PM1-4-4
PIN Photodiode Emitter For 32 GBd 16QAM Wireless Link At 300 GHz
Simon Nellen; Carlos Castro; Lars Liebermeister; Robert B. Kohlhaas; Robert Elschner; Colja Schubert; Martin Schell; Bjoern Globisch; Bjoern Globisch; Ronald Freund
Fraunhofer HHI, Germany

We demonstrate a wireless data link at 300 GHz employing a broadband PIN photodiode as the emitter. With a symbol rate of 32 GBd and QPSK modulation error-free transmission at a gross data rate of 64 Gbit/s is achieved. For 16QAM modulation, forward error correction enables a net data rate of 100 Gbit/s, which is among the highest values reported so far.

15:15 Tu-PM1-4-5
300 GHz Wireless Communication Systems Exploiting The Benefits Of Combining Photonic And Electronic Transceiver Components
Ingmar Kalfass¹; Iulia Dan¹; Pascal Szriftgiser²; Vinay-Kumar Chini³; Mohammed Zaknoune³; Guillaume Ducournau^3
1Institute of Robust Power Semiconductor Systems, Univ Stuttgart, Germany; ²PhLAM, France; ³IEMN CNRS/Université de Lille, France

The contribution presents a wireless data transmission experiment combining photonic and electronic technologies. The photonic transmitter is based on the use of uni-traveling-carrier (UTC) photodiodes. The electronic receiver is based on multi-functional monolithic integrated circuits realized in high electron mobility transistor (HEMT) technology for low-noise pre-amplification as well as integrated I/Q detection. The combination of both is interesting towards the achievement of larger distances and high data-rates for future THz links. In this paper we present an initial experiment where 80 Gbit/s were achieved, carried out in the context of a join French-German research initiative.

15:30 Tu-PM1-4-6
300 GHz-band 50 Gbit/s Dual Channel Link Using Industrial Silicon Photonics Technology
Cybelle Belem¹; Elsa Lacombe²; Vincent Gidel²; Cedric Durand²; Frederic Gianesello²; Daniel Gloria²; Cyril Luxey³; Guillaume Ducournau^1
1IEMN CNRS/Université de Lille, France; ²STMicroelectronics, France; ³Polytech'Lab, Univ Nice Sophia, France

We demonstrate the use of an industrial silicon photonics photodiode towards indoor THz links in the 300 GHz band. The devices are presented and two links are reported: the first one in a single channel operation QPSK-25 Gbit/s signaling and the second one using a dual channel configuration, 260 and 280 GHz, reaching 50 Gbit/s. In each case, the detection is done using a III-V GaAs Schottky-based sub-harmonic mixer.

15:45 Tu-PM1-4-7
Millimeter Wave Vacuum Electronic Amplifiers For High Data Rate Communication
PAN PAN; Zhangxiong Zi; Ji Chen; Shishuo Liu; Qingmei Xie; Ye Tang; Jun Cai; Jinjun Feng
Beijing Vacuum Electronics Research Institute, China

Traveling wave tubes, one kind of vacuum electronic amplifiers, have been widely used in radars and satellite communications. For its capability to provide high output power in millimeter wave regime, traveling wave tubes are an enabling technology for outdoor long-range high data rate communication. Traveling wave tubes operating at E-band, W-band and G-band are being developed and the experimental results of prototypes are presented.

14:00 - 16:00 Tu-PM1-5 Nano-quantum Devices 1

Chairperson: Room 101

14:00 Tu-PM1-5-1

Ultra-Small Mode Volume Three-Dimensional THz LC Metamaterial
Mathieu Jeannin¹; Djamal Gacemi¹; Angela Vasanelli¹; Lianhe Li²; Edmund Linfield²; Carlo Sirtori¹; Yanko Todorov^1
1Ecole Normale Supérieure, France; ²School of Electronics and Electrical Engineering, University of Leeds, United Kingdom

We present a novel architecture for THz metamaterials relying on three-dimensional meta-atoms embedding a semiconductor active region. The meta-atoms behave as inductor-capacitive (LC) resonators with nano-scale capacitive parts, and they have extremely sub-wavelength mode volume (10^-6λ_0) and footprint (10^-3λ_0^2). When the LC resonators are coupled to a two-dimensional electron gas confined inside the capacitive elements the ultra-strong light-matter coupling regime is achieved. We also discuss the potential of such structures for ultra-low dark current THz quantum well photodetectors.

14:30 Tu-PM1-5-2
High Performance Graphene Ballistic Rectifiers For THz Detection
Jiawei Zhang; Joseph Brownless; Aimin Song
University of Manchester, United Kingdom

Although graphene can operate in the ballistic transport regime at room temperature, there are very few devices harnessing this property. Here we present a novel device called the ballistic rectifier which circumvents the problem of opening a bandgap in graphene. Based on the device theory, we proposed four different asymmetric planar structures. All devices are working and showed responsivity higher than 1,000 V/W at room temperature, with noise-equivalent power as low as 4.16 pW/Hz^1/2. These properties make GBRs a suitable candidate for THz detections.

14:45 Tu-PM1-5-3
Ultrastrong Coupling Of Plasmonic Metamaterials And Photons In A Terahertz Photonic Crystal Cavity
Fanqi Meng; Mark D. Thomson; Bernhard Klug; Dovilė Čibiraitė; Qamar ul-Islam; Hartmut G. Roskos
J. W. Goethe-Uni Frankfurt, Germany

Here, we report a new type of strong light-matter interaction of metamaterial 'quasi-particles' with photons in a photonic crystal cavity in the terahertz frequency range. The measured Rabi splitting shows a square-root dependence on the density of metamaterial unit cells, even for unit cells from two spatially separated planar metamaterials, indicating nonlocal collective strong interactions. These findings are of interest for the investigation of fundamental strong-coupling phenomena, but also for applications such as ultra-low-threshold terahertz polariton lasing, voltage-controlled modulators and frequency filters, and ultra-sensitive chemical and biological sensing.

15:00 Tu-PM1-5-4
Towards Millimeter-Wave Based Quantum Networks
Hubert Stokowski¹; Marek Pechal¹; Emma Snively²; Kevin Multani¹; Paul Welander²; Jeremy Witmer¹; Emilio Nanni²; Amir Safavi-Naeini^1
1Stanford University, United States; ²SLAC National Accelerator Laboratory, United States

Realization of quantum networks composed of superconducting microwave circuits acting as qubits recently gained tremendous attention as an effective way of scaling quantum computers. Here we present the first experimental approach to fabricate mm-wave superconducting resonators that could be combined with transmon qubits and used in future ÃfÆ'Ã?â?TÃfâ? Ã¢â,¬â"¢ÃfÆ'ââ,¬Â¦Ãfâ?sÃ,½ÃfÆ'Ã?â?TÃf¢ââ?s¬Ã.¡ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,¼m-mm converters that distribute entanglement at a high rate in low-loss quantum networks. We propose a method that facilitates a long-range spread of quantum information via direct coupling of such a device into W-band (75-110 GHz) waveguide.

15:15 Tu-PM1-5-5
Sliver Nanowire Surface Plasmon Polaritons Enhancement In Terahertz Nanodevices
Shihab Al-Daffaie¹; Oktay Yilmazoglu¹; Matthias Wiecha²; Amin Soltani²; Franko Küppers¹; Thomas Kusserow¹; Hartmut Roskos^2
1Technische Universität Darmstadt, Germany; ²Goethe-Universität, Germany

New types of continuous-wave (CW) THz photomixers were fabricated using a silver nanowire (Ag-NW) as nanocontact on low-temperature-grown (LTG) and nitrogen-ion-implanted GaAs, respectively. The Ag-NW nanoelectrodes produced a large reduction of the device capacitance and a significant enhancement of the photocurrent as compared to conventional photomixers. The combination of very low capacitance and high photocurrent are shown reliable and efficient THz generation in the upper part of the broad spectral THz range. The main enhancement is shown from the wave patterns of surface plasmon polaritons (SPPs) on the Ag-NW which are measured using a scattering-type Scanning Near-field Optical Microscope (s-SNOM).

15:30 Tu-PM1-5-6
Nano-FTIR Spectroscopy Of Intersubband Polaritons In Single Nanoantenna
Oleg Mitrofanov¹; Chih-Feng Wang²; Terefe Habteyes²; Willie Luk³; John Klem³; Hou-Tong Chen⁴; Igal Brener^3
1UCL, United Kingdom; ²University of New Mexico, United States; ³CINT, Sandia NL, United States; ⁴CINT, Los Alamos National Lab, United States

We demonstrate observation of infrared (IR) intersubband (ISB) polaritons in an isolated subwavelength size nanoantenna using near-field Fourier-transform infrared (FTIR) spectroscopy of the evanescent fields on the nanoantenna surface. The near-field approach enables detection of the distinctive polariton splitting of the nanoantenna resonance in the amplitude and phase spectra, as well as mapping of the ISB polariton dispersion. The nano-FTIR spectroscopy approach opens doors for investigations of light-matter interaction in the single subwavelength nanoantenna regime.

15:45 Tu-PM1-5-7
Semiconductor Quantum Plasmonics
Angela Vasanelli¹; Simon Huppert²; Andrew Haky¹; Yanko Todorov¹; Carlo Sirtori^1
1Ecole Normale Supérieure, France; ²Sorbonne Université, France

We investigate the effect of quantum confinement on plasmons in highly doped semiconductor layers. The collective response of the electron gas is constructed from the basis of the confined electronic wavefunctions, accounting for dipole-dipole coupling and non-parabolicity. Our work shows how quantum engineering can be applied to semiconductor plasmonics.

14:00 - 16:00 Tu-PM1-6 Metamarials 2

Chairperson: Aydin Babakhani Room 151

14:00 Tu-PM1-6-1

Spectroscopic Evidence Of Bloch Surface Waves In The Mid Infrared
Michele Ortolani¹; Marialilia Pea²; Agostino Occhicone³; Valeria Giliberti⁴; Alberto Sinibaldi³; Francesco Mattioli²; Sara Cibella²; Raffaella Polito¹; Alessandro Nucara¹; Leonetta Baldassarre¹; Francesco Michelotti^3
1Sapienza University of Rome, Dipartimento di Fisica, Italy; ²Consiglio Nazionale delle Ricerche (CNR), Italy; ³Sapienza University of Rome, Dipartimento SBAI, Italy; ⁴Istituto Italiano di Tecnologia, Center for Life Nanoscience, Italy

Bloch Surface Waves (BSWs) are surface electromagnetic waves with very low intrinsic losses, existing in both in-plane and out-of plane polarizations, supported by a one-dimensional photonic crystal with an in-gap defect. We have developed thin film deposition technology on CaF2 prisms suitable for biosensing applications of BSWs in the mid-infrared. Here we report spectroscopic evidence of BSWs, in perfect agreement with theory, in the wavelength range from 4 to 6 micrometers. In summary, we envisage Surface Plasmon Polarioton-like biosensing applications, in which the mid-IR fingerprints of thin samples located at the interface are detected with high sensitivity by Bloch Surface Waves instead of SPPs.

14:30 Tu-PM1-6-2
High Q-factor Coupled Fabry-Perot Plasmonic Nanoresonator
Baptiste FIX¹; Julien Jaeck¹; Patrick Bouchon¹; Nathalie Bardou²; Sébastien Héron¹; Benjamin Vest¹; Haïdar Riad^1
1ONERA, France; ²C2N-CNRS, France

Fabry-Perot (FP) like resonances have been widely described in nanoantennas. In the case of combination of nanoantennas, it has been reported that each cavity behaves independently. Here, we evidence the interferences between two FP absorbing nanoantennas, which has a strong impact on the optical behavior. While the resonance wavelength is only slightly shifted, the level of absorption reaches nearly 100%. Moreover, the quality factor increases up to factor 7 and can be chosen by geometric design over a range from 11 to 75. We first demonstrate thanks to a simple analytical model that this coupling can be ascribed to a double FP cavity resonance, with the unique feature that each cavity is separately coupled to the outer medium. Based on this principle, we experimentally illustrate the existence of a high-Q factor resonance originating from the interference between two under-coupled ribbon-shaped nano Fabry-Perot.

14:45 Tu-PM1-6-3
Study Of Terahertz High Q-factor All-Dielectric Metamaterials
Xiaoyong He; Jun Peng
Mathematics & Science College, Shanghai Normal University, China

The propagation properties of Si based all-dielectric metamaterials (ADMs) structure have been investigated systematically in the THz regime. The results manifest that ADMs indicate sharp resonant curves with large Q-factors of more than 60, and figure of merit is about 20. Compared with that of metal metamaterials counterparts, the thickness of ADMs (in the range of tens of micrometers) is much larger to excite obvious resonant curves. With the help of a uniform graphene layer, the resonant curves can also be flexible modulated in a wide range, the amplitude modulation depth can reach about 40%. The results are very useful to design high Q-factor dielectric devices in the future, e.g. biosensors, modulators, and filter.

15:00 Tu-PM1-6-4
Modes And Pseudo-modes In TE Extraordinary THz Transmission
Suzanna Freer¹; Miguel Camacho²; Sergei A Kuznetsov³; Eve Shalom¹; Jack Gape¹; Rafael R Boix⁴; Miguel Beruete⁵; Miguel Navarro-Cia^1
1University of Birmingham, United Kingdom; ²University of Exeter, United Kingdom; ³Rzhanov Institute of Semiconductor Physics SB RAS Novosibirsk Branch TDIAM, Russian Federation; ⁴University of Seville, Spain; ⁵Universidad Pública de Navarra, Spain

Transverse electric (TE) transmission through dielectric-backed subwavelength slit arrays is inextricably linked to the grounded-dielectric slab TE1 mode, and thus, it depends highly on the electrical thickness of the substrate. We track the influence of the TE1 mode using both Terahertz time domain spectroscopy (TDS) measurements and the Method of Moments. For electrically thick dielectric samples, the TE1 mode is in propagation, and hence total transmission occurs (in excess of 0 dB, attributed to collimation), whereas in electrically thin samples, the TE1 mode is in cutoff. In this regime, the mode still contributes to transmission, and hence is referred to as a pseudo-mode.

15:15 Tu-PM1-6-5
Fano Resonance In Terahertz Superconducting Tl2Ba2CaCu2O8 Metamaterials
Jingbo Wu¹; Yun Guan¹; Jian Xing²; Lu Ji²; Caihong Zhang¹; Huabing Wang¹; Biaobing Jin¹; Jian Chen¹; Peiheng Wu^1
1Nanjing University, China; ²Nankai University, China

Tl2Ba2CaCu2O8 is layered cuprate superconductor with high anisotropy. Using Tl2Ba2CaCu2O8 film and asymmetric resonator structure, we designed and fabricated a kind of terahertz metamaterials. The tuning of the Fano-type resonance with the change of temperature is experimentally demonstrated.

15:30 Tu-PM1-6-6
Manipulation On Terahertz Slow Light In Symmetry Broken Meta-molecules
Zhenyu Zhao¹; Wei Peng²; Jianbing Zhang^2
1Shanghai Normal University, China; ²Chinese Academy of Sciences, China

We investigate slow light effect owing to the plasmon-induced transparency (PIT) via symmetric breaking in terahertz meta-molecules (MM). A broadband PIT window as well as a localized slow light effect is achieved via conductively coupled dimer and trimer MM.

15:45 Tu-PM1-6-7
Ultrastrong Coupling Experiments With Superradiant Meta-atoms
Moritz Wenclawiak; Benedikt Limbacher; Aaron M. Andrews; Gottfried Strasser; Karl Unterrainer; Juraj Darmo
TU Wien, Austria

In this contribution, we study the effects arising when using a metamaterial surface featuring a dense array of superradiant emitters as cavities for experiments in the ultrastrong coupling regime. We show that an increasing cavity loss does not always lead to the expected transition to the weakly coupled Purcell regime but more that it is still possible to observe polaritons as a feature of the strong coupling between the meta-atoms and the intersubband transition.

15:45-16:15 - Coffee Break

16:30-18:15 Parallel sessions Tu-PM2

16:30 - 18:15 Tu-PM2-1 Films and Coatings

Chairperson: Michael Johnston Amphi Lavoisier

16:30 Tu-PM2-1-1
Investigation Of Multilayered 20th Century Painting By THz Imaging
Kaori Fukunaga¹; Yoshimi Ueno²; Yasunobu Ito^3
1National Institute of Information and Communications Technology, Japan; ²CRS Corporation, Japan; ³Ikea Museum of 20th Century Art, Japan

A masterpiece of Salvador Dali was investigated by using Terahertz time-domain imaging. The experimental results confirmed its multilayered structure and suggested that Dali did not cover the entire canvas because the number of painted layers depends on the area. The painting was supported with a lining layer and a metal plate added in previous intervention, and its structure was compared with that of another 20th century masterpiece painted by Pablo Picasso.

17:00 Tu-PM2-1-2
Mobile Handheld FMCW Terahertz Multilayer Thickness Inspection
Nina Schreiner; Stefan Weber; Andreas Keil; Fabian Friederich
Fraunhofer ITWM, Germany

We present an all-electronic handheld system for the thickness determination of dielectric multilayer structures with submillimeter to several centiÃ,¬meter layer thicknesses, using a frequency-modulated continuous-wave terahertz transceivers. Besides A-scans, an integrated linear position encoder allows to obtain B-scan images. In order to resolve layers below the inherent resolution limit given by the frequency modulation bandwidth, we take advantage of model-based signal processing techniques.

17:15 Tu-PM2-1-3
Ancient Painting On Copper Substrate Inspected By Terahertz Spectroscopy-imaging
Quentin Cassar¹; Corinna Koch-Dandolo²; Jean-Paul Guillet¹; Marie Roux³; Frédéric Fauquet¹; Patrick Mounaix^1
1Laboratoire IMS / Université de Bordeaux / CNRS UMR 5218, France; ²C2MRF / Palais du Louvre, France; ³L'Atelier des Renaissances, France

We used a combination of numerical simulation to find parameters that best describe reflections from a given multi-layered paint sample. The reflected terahertz time domain waveform is simulated where each paint layer is represented by a set of numerical parameters that describe both the thickness and the optical response. We detected numerous sketches under the painting layers.

17:30 Tu-PM2-1-4
Operational Readiness Levels For Terahertz Automotive Paint Inspection
Robert May; Ian Gregory; Daniel Farrell
TeraView Ltd., United Kingdom

The demanding requirements placed on industrial test equipment means that for terahertz sensing to be adopted in quality control sectors, the technology must not only be capable of providing the qualitative and/or quantitative information of interest, but to do so in a robust and reliable manner. Here, we report on some of the developments implemented to bridge this gap for terahertz sensing to be deployed into one such industrial production setting: coating thickness inspection in the automotive paint shop. This has allowed terahertz to provide feedback on paint film thicknesses, and thereby allow for greater control of the paint process. Application Readiness, as defined by key manufacturers, their distributors and integrators, has been achieved.

17:45 Tu-PM2-1-5

Terahertz Non-Destructive Thickness Characterization Of Optically Thin Wu?stite Layers On Steel
David Citrin¹; Alexandre Locquet¹; Roquelet Cyrielle²; Min Zhai^1
1Georgia tech Lorraine, France; ²ArcelorMittal Maizières Research, France

Terahertz (THz) imaging is a relatively new technique for nondestructive evaluation. Compared with the destructive micro-cut technique that provides information along the line of cut only, THz imaging nondestructively provides a global mapping of a sample. Hence, this technique has been applied to characterize coated materials and composite laminates. In this work, we characterize optically thin wüstite layers on steel leveraging signal-processing techniques.

18:00 Tu-PM2-1-6

Learning-Based Shadow Mitigation For Terahertz Multi-Layer Imaging
Pu (Perry) Wang¹; Toshiaki Koike-Akino¹; Arindam Bose²; Rui Ma¹; Phillip Orlik¹; Wataru Tsujita³; Kota Sadamoto³; Hiroyuki Tsutada^3
1Mitsubishi Electric Research Laboratories, United States; ²University of Illinois at Chicago, United States; ³Mitsubishi Electric Corporation Advanced Technology R&D Center, Japan

This paper proposes a learning-based approach to mitigate the shadow effect in the pixel domain for Terahertz Time-Domain Spectroscopy (THz-TDS) multi-layer imaging. Compared with model-based approaches, this learning-based approach requires no prior knowledge of material properties of the sample. Preliminary simulations confirm the effectiveness of the proposed method.

16:30 - 18:30 Tu-PM2-2 Applications 1

Chairperson: René Beigang Petit Amphi

16:30 Tuo-PM2-2-1
Remote Liquid Inspection With Carbon Nanotube Terahertz Detectors
Meiling Sun; Kou Li; Yu Tokumoto; Ryogo Utaki; Yukio Kawano
Tokyo Institute of Technology, Japan

High installation cost, low temperature operation and strict measuring condition have been technical difficulties on terahertz (THz) wave inspections, which severely pulled back the development of THz wave application in real life. Here, to realize much quicker and lower-cost quality inspection in terahertz region, we developed a novel type of compact remote quality inspection system without conventional bulky THz time-domain spectroscopy (THz-TDS) system by utilizing a thermoelectric THz imager based on carbon nanotube (CNT) films. The present scheme enabled us to realize well applicable THz wave inspections.

17:00 Tu-PM2-2-1
Terahertz Diagnostics At Accelerators Using Radio Frequency-driven Frequency Combs Based On Telecommunication Technology
Erik Bruendermann¹; Johannes Leonhard Steinmann¹; Isao Morohashi²; Shinya Nakajima²; Shingo Saito²; Norihiko Sekine²; Anke-Susanne Mueller¹; Iwao Hosako^2
1Karlsruhe Institute of Technology / IBPT, Institute for Beam Physics and Technology, Germany; ²National Institute of Information and Communications Technology, Japan

We report on exploiting information and communications technologies to build reliable and durable terahertz diagnostics for electron accelerator-based light and laser sources. Terahertz and electro-optical diagnostics is an ideal tool to investigate short-bunch electron beams and their emitted photons with the potential to devise methods for controlled and tailored radiation emission. We investigate electro-optical modulators to evaluate their potential for laser-based diagnostics at accelerators, which can serve as building blocks in frequency combs, terahertz generation and detection systems. We built a frequency comb spanning at least 250 GHz with a pulse length of less than 3.7 ps.

17:15 Tu-PM2-2-3
Spoilage Of Salmon Fillets As Observed By THz Waves
Francis Hindle¹; Lotta Kuuliala²; Meriem Mouelhi¹; Arnaud Cuisset³; Mathias Vanwolleghem⁴; Frank Devlieghere⁵; Gael Mouret³; Robin Boquet^3
1Laboratoire de Physico-Chimie de l'Atmosphère, Université du Littoral Côte d'Opale, France; ²Research Unit Food Microbiology and Food Preservation, Department of Food Technology, Ghent University, Belgium; ³Laboratoire de Physico-Chimie de l'Atmosphère, France; ⁴Institute of Electronics, Microelectronics and Nanotechnology, University of Lille, France; ⁵Research Unit Food Microbiology and Food Preservation, Ghent University, France

The minimization of food wastage is an important challenge for today's society. Microbial activity during the storage of foodstuffs packed under a protective atmosphere, will lead to the generation of a complex mixture of trace gases that may be used as food spoilage indicators. THz waves have been used to monitor the generation of hydrogen sulfide in the headspace of a sealed plastic tray containing a salmon fillet portion.

17:30 Tu-PM2-2-4
Towards Detection Of Helical Orientated Cellulose Structures In Wood Using THz Time-Domain Spectroscopy
Jingming Cao¹; Markus Rüggeberg²; Peter Zolliker^3
1Laboratory for Transport at Nanoscale Interfaces/ Empa-Swiss Federal Laboratories for Materials Sci, Switzerland; ²Institute for Building Materials/ETH Zürich-Swiss Federal Institute of Technology, Switzerland; ³Laboratory for Transport at Nanoscale Interfaces/Empa - Swiss Federal Laboratories for Materials Sci, Switzerland

Wood is a fiber-reinforced, orthotropic composite material, which shows complex anisotropic optical characteristics induced by the preferential orientation of the cellulose microfibrils in the THz domain. We hypothesize that in addition to their birefringent properties the helical arrangement of microfibrils could also exhibit optical activity. This would allow determining microfibril angles in wood, a key feature for its mechanical properties. We propose to detect optical activity and birefringence independently using THz time-domain spectroscopy (THz-TDS) despite interference with annual ring structure. Our procedure is based on the Jones calculus formalism. In this report, we demonstrate the ability to detect left- and right-handed chirality of prototype helical structures made of copper wires and birefringence of spruce wood.

17:45 Tu-PM2-2-5
Industrial Applications With Semiconductor-Based CW Terahertz System
Eui Su Lee; Mugeon Kim; Dong Woo Park; Kiwon Moon; Il-Min Lee; Hyun-Soo Kim; Dong Hun Lee; Kyung Hyun Park
ETRI, Republic of Korea

In developing terahertz (THz) technologies that are more suitable for industrial applications, we have focused on research on continuous-wave (CW) THz technologies to develop small, low-cost, and multifunctional THz devices and systems. In this study, we present an example of a practical industrial application of our CW THz system, a nondestructive evaluation (NDE) system: cost-effective high-speed 1-D/2-D reflective imaging system and real-time thickness monitoring system of slurry film. Although further improvements to photonics-based THz technologies are necessary, we believe that efforts in this field will begin an era of THz technologies as a widely-used industrial technique.

18:00 Tu-PM2-2-6
Inspection Of Oils, Caffeine Containing Foods And Consumable Plant Leaves By Time-domain THz Spectroscopy
Mindaugas Karaliūnas¹; Ignas Dapsys²; Andrzej Urbanowicz¹; Gytis Vektaris³; Ausra Vektarienė³; Dalia Brazinskienė¹; Svajus Asadauskas¹; Irmantas Kasalynas¹; Gintaras Valusis^1
1Center for Physical Sciences and Technology, Lithuania; ²Department of Mathematical Modeling, Vilnius Gediminas Technical University, Department of Mathematical Modeling, Lithuania; ³Institute of Theoretical Physics and Astronomy, Vilnius University, Lithuania

Terahertz (THz) spectroscopy is a very promising and practical method for rapid and reliable food quality inspection. However, the issues related to water absorption, scattering of the medium and unambiguous detection of extremely small concentration of contaminants need to be overcome. This work show the capabilities of THz time domain spectroscopy to identify the contaminated and adulterated foods. The performance of this technique is studied on edible oils, caffeine containing foods and consumable plant leaves.

16:30 - 18:15 Tu-PM2-3 THz Devices 2

Chairperson: Iwao Hosako Room 162

16:30 Tu-PM2-3-1

Terahertz Beam Steering Based On Luneburg Lens
Kazuto Sato; Yasuaki Monnai
Keio University, Japan

A novel method of terahertz beam steering using a Luneburg lens is proposed. Based on the nature of the transverse electric wave propagation between parallel plates, we design a Luneburg lens operating around 300 GHz. We experimentally demonstrate the generation of a directional beam from the lens into free-space. We also show that the beam deflection can be changed by tilting the lower plate of the parallel plates.

17:00 Tu-PM2-3-2
Dielectric-Grating In-Lens Polarizer For Beyond 5G Communications
Marta Arias Campo¹; Giorgio Carluccio²; Darwin Blanco³; Simona Bruni⁴; Oliver Litschke⁴; Nuria Llombart^1
1Delft University of Technology, Netherlands; ²NXP Semiconductors, Netherlands; ³Ericsson AB, Sweden; ⁴IMST GmbH, Germany

A high-gain broadband leaky-wave fed lens antenna with an integrated dielectric gratings polarizer covering the whole G-band (140-220GHz) is presented. This work focuses on the polarizer gratings manufacturing and in particular on the selection of plastic materials and the fabrication process refinement. The polarizer geometry has been designed and optimized to be compatible with standard milling techniques. A quasi-analytical method based on an analysis of the lens antenna in reception is used to validate the in-lens polarizer performance. Several prototypes have been fabricated, finally obtaining an excellent match between measurements and quasi-analytical results.

17:15 Tu-PM2-3-3
Low-loss Planar Porous Components For Terahertz Beamforming
Hichem Guerboukha¹; Kathirvel Nallappan¹; Yang Cao¹; Mohamed Seghilani²; Jose Azana²; Maksim Skorobogatiy^1
1Polytechnique Montreal, Canada; ²INRS-EMT, Canada

We develop planar porous components to solve the loss problem of conventional convex optics. We show that by introducing deeply subwavelength pores in a dielectric substrate, we can fabricate a porous lens and an OAM phase plate with lower loss than their all-solid counterparts.

17:30 Tu-PM2-3-4
Characterization Of A Terahertz Isolator Using A 1.5 Port Vector Spectrometer
Fahd Rushd Faridi; Sascha Preu
Technische Universität Darmstadt, Germany

The 1.5 port vector spectrometer combines both transmission and reflection geometry of terahertz time domain spectroscopy (THz TDS) in a single setup. Here we demonstrate its capability for characterizing a non-time invariant device - a terahertz isolator, in terms of isolation level and insertion loss.

17:45 Tu-PM2-3-5
Quasi-Analytical Description Of A Double Slit Planar Dielectric Waveguide As Broadband Dispersion Compensating Element
Mario Méndez Aller; Sascha Preu
Technische Universität Darmstadt, Germany

We demonstrate dispersion compensation of dielectric waveguides by a double slit dielectric structure by a quasi-analytical solution. The concept is then confirmed with a full-wave numerical simulation of realistic rectangular waveguides.

18:00 Tu-PM2-3-6
Device For Broadband THz Spectroscopy Of 1-nL-volume Samples
Sergey Mitryukovskiy; Mélanie Lavancier; Flavie Braud; Théo Hannotte; Emmanuel Dubois; Jean-François Lampin; Romain Peretti
IEMN CNRS/Université de Lille, France

We report on our recent progress in the development of a device for light-matter interaction enhancement in the full terahertz range for precise spectroscopy of minor-volume samples. The efficient confinement of a broadband terahertz pulse to a few-nL-volume was achieved, opening new perspectives for chemical and biological applications. We discuss modifications in the fabrication process leading to the improvement of our technique, following the detailed characterization of the device performances.

16:30 - 18:15 Tu-PM2-4 Biology / Medicine 1

Chairperson: Emma MacPherson Room 269

16:30 Tu-PM2-4-1
Genomic Mechanisms Of THz-Induced Cancer Dysregulation In Human Skin
Cameron Hough¹; David Purschke¹; Chenxi Huang¹; Lyubov Titova²; Olga Kovalchuk³; Brad Warkentin¹; Frank Hegmann^1
1University of Alberta, Canada; ²Worcester Polytechnic Institute, United States; ³University of Lethbridge, Canada

Intense pulses of THz radiation significantly alter gene expression and dysregulate phenotypic endpoints of cancer-related signaling pathways, including activation of an inflammatory response and suppression of pro-mitotic signaling in human skin. Of 1681 potential candidates, the predicted cancer-related dysregulation is nearly entirely localized to a subset of only 42 key driver genes belonging to 7 gene families/superfamilies. The individual and concerted regulatory roles of these genes within the relevant cancer-related pathways are elucidated and discussed in the context of gene-specific response to THz exposure and potential for clinical application.

17:00 Tu-PM2-4-2
Do Humans "shine" In The Sub THz?
Yuri Feldman¹; Ksenia Baksheeva²; Roman Ozhegov²; Gregory Goltsman²; Nikolay Kinev³; Valery Koshelets³; Anna Kochnev¹; Noa Betzalel¹; Alexander Puzenko¹; Paul Ben Ishai^4
1The Hebrew University of Jerusalem, Israel; ²Moscow State University of Education, Russian Federation; ³Kotel'nikov Institute of Radio Engineering and Electronics of RAS, Russian Federation; ⁴Ariel University, Department of Physics, Israel

Radiometry experiments, performed on human subjects, show that in the vicinity of a central frequency 507 GHz the emission of the human skin is substantially non-equilibrium in its nature. The intensity of the radiation registered using a superconducting integrated receiver (SIR) [1], was correlated with the level of the physical and mental stress of subject under examination. This result suggests that human skin may generate sub-THz waves.

17:15 Tu-PM2-4-3
The Study Of The Optical Properties Of Serous And Mucous Tissues Of The Human Stomach
Roman Grigorev¹; Anna Kuzikova¹; Anna Kurasova¹; Petr Demchenko¹; Artyom Senyuk²; Abdo Khamid²; Mikhail Khodzitsky^1
1ITMO University, Russian Federation; ²Pavlova First St. Petersburg State Medical University, Russian Federation

The optical properties of mucous and serous fresh tissues of stomach were obtained using the method THz time-domain spectroscopy in the reflection mode. The difference in the optical properties of the two types of stomach tissue can be explained by their different morphology. The data may be used for intraoperative and endoscopic diagnostics of cancer.

17:30 Tu-PM2-4-4
Measurements Of Effective Porosity Of Pharmaceutical Tablets Using THz TDS
Iliya Tikhomirov¹; Daniel Markl²; Mira Naftaly^1
1National Physical Laboratory, United Kingdom; ²Strathclyde University, United Kingdom

The pharmaceutical industry requires a rapid nondestructive technique for monitoring porosity of tablets. Here porosity of compressed lactose pellets was investigated using THz time-domain spectroscopy (THz TDS) with the aid of index-matching medium.

17:45 Tu-PM2-4-5
Quasi-one-dimensional Terahertz Phononic Band Gap In Phospholipid Tails
Kaicheng Wang¹; Jingchao Tang¹; Jialu Ma¹; Lianghao Guo¹; Yang Yang¹; Wenfei Bo¹; Zhe Wu¹; Zhao Wang¹; Haibo Jiang²; Baoqing Zeng¹; Yubin Gong^1
1University of Electronic Science and Technology of China, China; ²Chengdu Institute of Biology, Chinese Academy of Sciences, China

Terahertz vibrational modes and quasi-one-dimensional terahertz phononic band gap in hydrocarbon tails of phospholipids are revealed through vibration calculation based on the ab initio density functional theory (DFT). We get the correlation between vibrational modes and frequencies. The phononic band gap in linear hydrocarbon chains provides a perspective in the interpretation of biochemical phenomena related to biological membranes, such as the photosynthetic energy transfer pathway and the electron transport chain in the inner mitochondrial membrane.

18:00 Tu-PM2-4-6
Non-Destructive Characterization Of Pharmaceutical Tablets Using Terahertz Frequency Domain Spectroscopy
Anis MoradiKouchi¹; Marin Lindsjö²; Jan Stake¹; Staffan Folestad²; Helena Rodilla^1
1Chalmers University of Technology, Sweden; ²AstraZeneca, Sweden

In this paper, terahertz frequency domain spectroscopy (THz-FDS) technique has been employed to study the impact of porosity in tablets on their optical constants, such as the effective permittivity. Four sets of training tablets with different percentage of active ingredient and compaction force were generated with microcrystalline cellulose (MCC) as the excipient and indomethacin as the active pharmaceutical ingredient. The results show that the extracted effective permittivity is sensitive to the change of porosity in tablets and it is unique for different concentration of indomethacin. Therefore, THz-FDS technique has been revealed to be a promising tool in the quality inspection of pharmaceutical tablets.

16:30 - 18:15 Tu-PM2-5 Materials 2

Chairperson: Patrick Mounaix Room 101

16:30 Tu-PM2-5-1
Can We Observe Vibrational Confinement In Lyophilised Proteins Using Terahertz Spectroscopy?
Talia Shmool; J. Axel Zeitler; Markus Leutzsch; Michael D. Mantle
Department of Chemical Engineering and Biotechnology, University of Cambridge, United Kingdom

Abstract-The purpose of this work was to use terahertz time-domain spectroscopy (THz-TDS) to investigate the vibrational dynamics of freeze-dried protein formulations and the behaviour of these materials below and above the glass transition temperature. In contrast to small organic molecules and polymers which exhibit continuously increasing absorption with temperature, a number of lyophilised formulations examined in this work show a plateau of absorption above 300 K. This plateau suggests that at high temperatures the protein molecules are confined in the surrounding excipient matrix. This vibrational confinement in the solid-state is uniquely observed using THz-TDS, and this work could provide insight into predicting formulation stability.

16:45 Tu-PM2-5-2
Broadband Spectroscopy Of Materials With An Integrated Comb-Based Millimeter-Wave Detector
Babak Jamali; Jiashu Zhou; Aydin Babakhani
University of California, Los Angeles, United States

A miniaturized broadband spectroscopic sensor using a fully integrated millimeter-wave detector is presented. The detector chip generates a frequency comb with a tunable spacing as a reference to downconvert received signals. By tuning the comb spacing, the detector can detect frequency tones from 50 GHz to 155 GHz with a resolution only limited to the line width. A spectroscopy setup including the detector and four sheets made of different materials is implemented to characterize the frequency response of materials in this frequency range.

17:00 Tu-PM2-5-3
THz Absorption And Refraction Of KTA Crystal At Low Temperatures
Zhiming Huang¹; Jingguo Huang¹; Yanqing Gao¹; Gaofang Li¹; Yury Andreev²; Grigory Lanskii²; Valery Losev^3
1Shanghai Institute of Technical Physycs, China; ²Institute of Monitoring of Climatic and Ecological Systems SB RAS, Russian Federation; ³Institute of High Current Electronics SB RAS, Russian Federation

There is a significant interest to determine potential of widely used UV - near IR nonlinear crystals for frequency conversion into the THz range. Potassium titanyl arsenate KTiOAsO4 (KTA) is one of them. Main its advantage in comparison with the other oxide nonlinear crystals such as LBO, BBO or KTP, is significantly higher second-order (d33=16.2 pm/V at 1.064 micronmeter in the mid-IR) nonlinear susceptibility and long (5.3 micronmeter at zero transmittance level) mid-IR cutoff wavelength. As for comparison with semiconductor nonlinear crystals, KTA crystal possesses muchhigher damage threshold. Refractive indices of KTA crystal at THz region were measured before only at room temperature. Here cryogenic THz spectrometer is designed with precision temperature control. Optical properties of KTA crystal (absorption coefficients and refractive indices) are investigated in detail with THz-TDS in the temperature range 5-300 K. Refractive indices can be approximated in the form of dispersion equations for different

17:15 Tu-PM2-5-4
Mechanism Between Material Microstructures And Terahertz Dielectric Properties
Bin Yang
University of Chester, United Kingdom

Significant progress has been made in developing reliable Terahertz (THz) measurement spectroscopy to extract materials' dielectric properties, however, systematic research on exploring intrinsic mechanism between microstructure of ceramics and THz dielectric properties such as loss, permittivity and dispersive characters has barely started. The paper focuses on one dielectric ceramic system (TiO2), its addition with Zn2SiO4 dielectrics and one hexa-ferromagnetic system to expatiate the association.

17:30 Tu-PM2-5-5
Time-resolved THz Spectroscopy Of Conducting Polymers
Jérôme Degert; Frédéric Dutin; Marc Tondusson; Eric Freysz
Université de Bordeaux - LOMA, France

We study, by terahertz time-domain and optical pump-THz probe spectroscopies, the optical and electrical properties of the PEDOT/PSTFSIK polymer. The latter is designed to get reed of some drawbacks of the well-known and widely used conducting polymer: the PEDOT/PSS. The optoelectronic properties in the THz range of both compounds are compared, as well as the relaxation mechanisms taking place after their photoexcitation by ultrashort optical pulses.

17:45 Tu-PM2-5-6
Dynamics Of Hydrogen Bonds And Cross-linked Structures In Polyurethane film Observed By Terahertz Spectroscopy
Hiromichi Hoshina¹; Yuichi Saito²; Takumi Furuhashi³; Tomomi Shimazaki³; Manabu Sawada³; Yasunori Hioki³; Chiko Otani^1
1RIKEN Center for Advanced Photonics, Japan; ²RIKEN, Japan; ³Murata Manufacturing Co., Ltd., Japan

Terahertz (THz) absorption spectra of the cross-linked polyurethane films are observed at the temperature between 30-180 °C. The obtained spectra show characteristic absorption band at 3 THz assigned as hydrogen bonded urethane group. Another band at 7 THz was assigned as intermolecular vibration of cross-linked structures between polymer chains. The temperature dependent spectra were analyzed by the perturbation correlation moving window two-dimensional spectroscopy (PCMW2D) to clarify the slight spectral change. The thermal behavior of the absorption intensities shows the dynamics of hydrogen bonds and cross-linked structures in the polyurethane films.

18:00 Tu-PM2-5-7
Temperature Dependent Giant Birefringence And Dichroism Of A BiFeO3 Single Crystal In The Terahertz Frequency
Zuanming Jin¹; Yuqing Fang¹; Xiumei Liu²; Jiajia Guo²; Yan Peng¹; Yiming Zhu¹; Zhenxiang Cheng³; Guohong Ma^2
1Shanghai Key Lab of Modern Optical System, and Engineering Research Center of Optical Instrument and, China; ²Shanghai University, China; ³University of Wollongong, Australia

THz time-domain spectroscopy (THz-TDS) is used to study the THz-optical properties of a single crystal bismuth ferrite (BiFeO3). The anisotropy of BiFeO3 is strongly dependent on the temperature. A giant birefringence is observed up to around 3.6.

18:30 Tu-PM2-5-8
Competing Interplay Of Photo-thermal And Photo-doping Effect During Light-induced Ultrafast Insulator-to-Metal Transition In VO2 Nanofilms At Terahertz Frequency
Zhaohui Zhai¹; Liang-Hui Du¹; Si-Chao Chen²; Li-Guo Zhu^1
1Institute of Fluid Physics, China Academy of Engineering Physics, China; ²Department of Optics and Optical Engineering, University of Science and Technology of China, China

The competing interplay of photo-thermal and photo-doping effect of VO2 nanofilm under fs laser excitation was studied at terahertz frequency. We find that with photo-thermal effect generated by fs laser pulses, both the character time constant of insulator-to-metal phase transition and the pump fluence threshold of transition were decreased, while the amplitudes of the two photo-response are competing.

16:30 - 18:15 Tu-PM2-6 Metamarials 3

Chairperson: Yiming Zhu Room 151

16:30 Tu-PM2-6-1
THz Resonances With Infinite Lifetime In Array Of Gold Resonators
Niels van Hoof¹; Stan ter Huurne¹; Diego Abujetas²; José Sanchez-gil²; Jaime Gómez Rivas^1
1Eindhoven University of Technology, Netherlands; ²Instituto de Estructura de la Materia Consejo Superior de Investigaciones Científicas, Spain

Metasurfaces consisting of two resonators per unitcell can support resonances with infinitely long lifetime known as bound states in the continuum. We investigate theoretically and experimentally the conditions leading to the formation of these resonances in gold particle arrays.

17:00 Tu-PM2-6-2
Broadband Terahertz Quarter-Wave Plate Design
Xiaolong You; Christophe Fumeaux; Withawat Withayachumnankul
The University of Adelaide, Australia

A broadband terahertz quarter-wave plate design based on an extended analytical approach has been presented and numerically demonstrated. The simulations reveal that this quarter-wave plate enables a linear-to-circular polarization conversion with a 3-dB axial ratio of 53.3%, ranging from 205 to 354 GHz. It is worth of noting that this presented approach has a potential to realize broadband transmissive metasurfaces for other wavefront and phase control functionalities, such as beam focusing, beam deflection, and polarization rotation.

17:15 Tu-PM2-6-3
Broadband And Wide—Angle Terahertz Reflective Half—Wave Mirror
Rajour Tanyi Ako¹; Wendy S. L. Lee²; Madhu Bhaskaran³; Sharath Sriram³; Withawat Withayachumnankul^2
1Functional Materials and Microsystems Research Group and the Micro Nano Research Facility, RMIT Univ, Australia; ²Terahertz Engineering Laboratory, School of Electrical and Electronic Engineering, The University of Adelaide, Australia; ³Functional Materials and Microsystems Research Group and the Micro Nano Research Facility, RMIT University, Australia

Linear—to—linear polarization conversion of electromagnetic wave has application in various fields including communications, imaging, and sensing. Available polarization-control devices enabled by metasurfaces are limited in bandwidth, efficiency and acceptance angle. Herein, a reflective half—wave mirror composed of T—shaped resonators is proposed and experimentally evaluated. Measured results show a bandwidth of 95% and 100% around a center frequency of 0.7 THz for the normal and 45° angle of incidence. The measured results agree well with the simulation. An average polarization conversion ratio (PCR) greater than 80% is observed across 0° to 45° incidence angles.

17:30 Tu-PM2-6-4
Femtosecond Laser Processing And Evaluation Of Broadband THz Anti-Reflection Structures
Haruyuki Sakurai; Natsuki Nemoto; Kuniaki Konishi; Ryota Takaku; Yuki Sakurai; Nobuhiko Katayama; Tomotake Matsumura; Junji Yumoto; Makoto Kuwata-Gonokami
The University of Tokyo, Japan

We fabricate terahertz anti-reflection structures on the surface of high-resistivity silicon via femtosecond laser processing, demonstrating broadband increase in transmissivity over 0.3 - 2.5 THz, and investigate the spectral characteristics by using numerical simulation. We successfully reproduce the observed result, and attribute transmittance drop-off in the higher frequency region to increasing material loss, not structural effects, induced by the laser-ablation fabrication process.

17:45 Tu-PM2-6-5
Free-standing Meta-surface On Ultrathin Si Substrate For High-transmission Phase Shifts In The 3.0-THz Band
Shohei Hayashi¹; Takehito Suzuki²; Kazunori Tanaka¹; Kazuki Horita¹; Hiroyasu Fujiwara¹; Kazuue Fujita^1
1Hamamatsu Photonics K.K., Japan; ²Tokyo University of Agriculture and Technology, Japan

We present a free-standing meta-surface for a high-transmission phase shift in the 3.0-THz band. The structure consists of subwavelength Au patterns with 278,273 units of meta-atoms on both the front and back of an ultrathin (4 µm thick) silicon substrate. The meta-surface for the low terahertz range has been fabricated by etching on a flexible polymer substrate with metal layers. High-precision fabrication of the meta-surface on a silicon substrate by semiconductor processing techniques is powerful and essential for the integration with terahertz semiconductor sources. Measurements by terahertz time-domain spectroscopy (THz-TDS) demonstrate a high transmission of 0.91 and a phase modulation of -0.86π at 2.8 THz agreeing well with simulations. The meta-surface in the high terahertz range can be applied in an ultrathin meta-lens for terahertz quantum cascade laser sources.

18:00 Tu-PM2-6-6
Broadband Terahertz Quarter-wave Plates Via Multipolar-interference-assisted All-dielectric Metamaterials
Da-Cheng Wang; Song Sun; Zheng Feng; Wei Tan
Microsystem and Terahertz Research Center, China

All-dielectric metamaterials with multipolar Mie resonances are proposed and experimentally realized, which operate as a broadband terahertz quarter-wave plate. Composed of elliptically-shaped silicon pillar arrays, the proposed metamaterials support dipole and quadrupole resonance modes. The constructive and destructive interferences among these modes could minimize reflection and maximize transmission. Both numerical and experimental results of the meta-device reveal close to unity transmission and 270 degrees phase delay between two orthogonal directions in a broadband, making the meta-device operate as a terahertz quarter-wave plate. Such multipolar-interference-assisted all-dielectric metamaterials promise a new paradigm for broadband low-loss terahertz devices.

18:15-19:30 - Poster session - Tu-Po 2 - Room 8

Tu-Po2-1
Enhanced Terahertz Emission Bandwidth From Photo-conductive Antenna With Embedded Plasmonic Nano-pillar Array
Arkabrata Bhattacharya; Dipa Ghindani; S. S. Prabhu
Tata Institute of Fundamental Research, India

In this work, we demonstrate a novel photo-conductive antenna (PCA) design, capable of emitting Terahertz radiation with enhanced bandwidth. This device consists of Au electrodes on semi-insulating GaAs substrate. A plasmonic nano-structure array is embedded in the substrate between the two electrodes. The role of this array is two-fold. The plasmonic enhancement of the 800 nm IR light near the nano-structures serves as a rich source of photo-generated charge carriers which are accelerated to generate the THz radiation. Secondly, the nano-structures acts as defect sites which enables fast carrier relaxations, hence, effectively enhancing THz bandwidths. At the same time the terminal currents are highly reduced implying robustness of the device to high applied bias voltages.

Tu-Po2-2
0.4 MW Terahertz Power Generation Through Bias-Free, Telecommunication-Compatible, Photoconductive Nano-Antennas
Deniz Turan; Nezih Tolga Yardimci; Mona Jarrahi
University of California, Los Angeles, United States

We present a bias-free, telecommunication-compatible, photoconductive terahertz source that generates terahertz powers as high as 0.4 mW, enabling time domain terahertz spectroscopy with up to 90 dB dynamic range over a 3.5 THz bandwidth.

Tu-Po2-3
Towards Bandwidth-enhanced GaN-based Terahertz Photoconductive Antennas
Dipa Ghindani¹; Arkabrata Bhattacharya²; Sumayya Samad³; Amit Shah⁴; Arnab Bhattacharya⁴; Shriganesh Prabhu^5
1Tata Institute of Fundamental Research, India; ²Tata Institute of Fundamental Research, Foton Lab, India; ³International School of Photonics, Cochin University of Science and Technology, CUSAT, India; ⁴Tata Institute of Fundamental Research, India; ⁵Tata Institute of Fundamental Research, Foton Lab, India

In this work, we explore a photoconductive antenna for the emission of Terahertz radiation based on Gallium Nitride (GaN) epilayers. Typically, GaN has faster carrier relaxation times as compared to SI-GaAs, which is conventionally used as substrate for conventional photoconductive antennas. Faster carrier lifetime is expected to result into enhanced bandwidth of the emitted THz radiation.

Tu-Po2-4
THz TDS System Driven By A Commercially Available Laser Diode
Jan Balzer¹; Sebastian Tonder¹; Jannik Lehr²; Martin Koch^2
1University Duisburg-Essen, Germany; ²Philipps University Marburg, Germany

We use a commercially available laser diode to drive a standard THz TDS system. The dispersion of the laser diode is compensated by a standard single mode fiber which leads to a pulse duration below 800 fs. The measured THz traces show frequency components up to 1 THz.

Tu-Po2-5
Effect Of Femtosecond Laser Polarization On Terahertz Emission From Cluster Nanoplasma
Nikolay Kuzechkin¹; Alexei Balakin¹; Murat Dzhidzhoev¹; Vyacheslav Gordienko¹; Igor Ivanov¹; Timur Semenov²; Alexander Shkurinov^1
1Lomonosov Moscow State University, Russian Federation; ²FSRC "Crystallography and Photonics" RAS, Russian Federation

We present the results of experimental studies of THz emission from argon cluster nanoplasma switched by the intense femtosecond laser pulses. We have performed measurements of the angular distribution of the THz radiation emitted from the clustered nanoplasma with two polarization states of the linearly polarized laser beam. We have found that polarization state of the laser radiation may influence on the efficiency of THz generation in cluster beam.

Tu-Po2-6
Direct Comparison Of PIN And UTC Photodiodes For Continuous-Wave Terahertz Emission
Simon Nellen¹; Tadao Ishibashi²; Lauri Maximilian Schwenson¹; Robert B. Kohlhaas¹; Lars Liebermeister¹; Steffen Breuer¹; Anselm Deninger³; Martin Schell¹; Bjoern Globisch^1
1Fraunhofer HHI, Germany; ²NTT Electronics Techno Corporation, Japan; ³TOPTICA Photonics AG, Germany

We provide the first-ever direct comparison of the terahertz (THz) output of fiber-coupled UTC- and PIN-based continuous-wave emitters. As both emitters are characterized in the same setup, the observed differences can be traced back to the diode structure itself. We find large differences for frequencies below 350 GHz, where each device excels in a certain spectral range. Between 350 GHz and 1 THz, both emitters achieve a comparable THz output.

Tu-Po2-7
Combined UTC-PD Integrated THz Source And A Leaky Wave Antenna With Complementary Split Ring Resonators Along A Planar Goubau Line
Tahsin Akalin¹; Abdallah Chahadih²; Ibrahim Türer³; Miguel Navarro-Cía⁴; Miguel Beruete⁵; Abbas Ghaddar^2
1Lille University, France; ²Lebanese University, Faculty of Science, section V, Lebanon; ³Airbus Defence and Space, Germany; ⁴University of Birmingham, School of Physics and Astronomy, United Kingdom; ⁵Universidad Pública de Navarra UPNA, Spain

We have fabricated a terahertz source based on the combination of an integrated Uni-Travelling-Carrier Photodiode (UTC-PD) and a leaky wave antenna. The UTC-PD is a broadband source and we have used an efficient transition from CPW to Planar Goubau Line (PGL). In this PGL section, we have included complementary Split Ring Resonators (c-SRR) in order to obtain a leaky wave antenna (LWA). The broadband behavior of the source and of the transition allow us to design systems at a given frequency range by modifying only the c-SRR along the PGL.

Tu-Po2-8
Different Plasmonic Regimes Of Laser-Plasma Terahertz Generation
Vasily Kostin¹; Irina Osovitskaya¹; Nikolay Vvedenskii^2
1University of Nizhny Novgorod, Russian Federation; ²Institute of Applied Physics, Russian Academy of Sciences, Russian Federation

The laser-plasma terahertz generation by one-color ultrashort ionizing pulses is studied using new model allowing the motion of the plasma electrons under forces both linear and quadratic in ionizing optical field. We determine different regimes of generation (with different plasmonic modes excited) and describe how the duration and phase structure of the ionizing pulse can affect not only the terahertz energy, but also the terahertz spectrum due to plasmonic effects.

Tu-Po2-9
A Cavity-coupled Microbolometer Terahertz Detector With A Metamaterial Reflector
Xuecou Tu; Peng Xiao; Zhihao Shao; Chengtao Jiang; Yaqian Wu; Xiaoqing Jia; Lin Kang; Jian Chen; Peiheng Wu
Nanjing University, China

In summary, we demonstrated a tunable Nb5N6 microbolometer with a movable MM reflector for THz detection. Continuous tuning over the free spectral range was achieved. The control of polarization is expected to aid the future implementation of our Nb5N6 microbolometers with broadband metamaterial polarizing reflector tuner structures. In addition, this type of structure has a good prospect in the large array of terahertz devices because of its easy integration and advantage in device packaging.

Tu-Po2-10
Possible Phonon-induced Electronic Bi-stability In VO2 For Ultrafast Memory At Room Temperature
Yong Tan¹; Hang Zhao¹; Liangliang Zhang²; Mostafa Shalaby²; Weber Cedric³; Yan Zhang²; Cunlin Zhang²; Acharya Swagata³; Cunningham Brian⁴; Gruning Myrta⁴; Kai Liu⁵; Mark Schilfgaarde^3
1Beijing Institute of Technology, China; ²Capital Normal University, China; ³King's College London, United Kingdom; ⁴School of Mathematics and Physics, Queen's University Belfast, United Kingdom; ⁵Tsinghua University, China

This concretely addresses a long-standing controversy on the role of phonons in the transition where the M1 phase of VO2 is a band insulator with a gap that is too large for pure many-body effects to stabilize a MIT without nuclear displacements.

Tu-Po2-11
Terahertz Generation In Gallium Nitride Quantum Wells
Abas Roble¹; Morgan Hibberd¹; Menno Kappers²; Rachel Oliver²; Darren Graham^1
1School of Physics and Astronomy & Phtoton Science Institute, The University of Manchester, United Kingdom; ²Department of Material Science and Metallurgy, University of Cambridge, United Kingdom

Terahertz emission spectroscopy was used to characterize InGaN/GaN and GaN/AlGaN quantum well structures grown along the polar c-axis and investigate the role of the built-in electrostatic fields in the generation of terahertz radiation. The fields were first calculated using a self-consistent k•Ã,p solver and compared to the magnitudes of the transient electric fields generated when the structures were excited in reflection geometry with femtosecond laser pulses.

Tu-Po2-12
Generation Of Spontaneous Parametric Down-converted Photons In The Sub-terahertz Frequency Range At 660nm
Bjoern Haase¹; Mirco Kutas¹; Felix Riexinger¹; Patricia Bickert¹; Andreas Keil¹; Daniel Molter¹; Michael Bortz¹; Georg von Freymann^2
1Fraunhofer ITWM, Germany; ²Department of Physics and Research Center OPTIMAS, Universität Kaiserslautern, Germany

There are two crucial steps towards terahertz quantum sensing. First, there is the challenge to deliver a source of entangled photons in the terahertz range. Second, measuring terahertz radiation using photons in a different spectral range has to be possible. As we generated entangled photons in the terahertz range by spontaneous parametric down conversion (SPDC), we received the first milestone. The detected signals matches both for down- and for up-conversion for forward as well as for backward terahertz radiation the calculated frequency angular spectrum both qualitative and quantitative. By observing difference frequency generation of external terahertz radiation with VIS pump photons, we achieved both steps towards terahertz quantum sensing.

Tu-Po2-13
Spatial And Temporal Field Evolution Of Evanescent Single-Cycle THz Pulses
Daniel Lake¹; Edward Snedden²; David Walsh²; Steven Jamison¹; Darren Graham^3
1Lancaster University, United Kingdom; ²Accelerator Science and Technology Centre, United Kingdom; ³The University of Manchester, The Photon Science Institute, United Kingdom

The temporal and spatial evolution of single-cycle THz pulses travelling across a dielectric boundary with effective surface velocity below c has been examined. The resulting subluminal evanescent waves in the near field vacuum region are potential drivers of particle accelerators. The electro-optic temporal and spatial imaging of the THz pulses emitted from the surface were measured in the near field, as a function of distance from the dielectric boundary, and reveal both temporal broadening and field decay that is dependent on the effective velocity of the wave in the plane of the boundary.

Tu-Po2-14
Lensless Infrared Image Processing Method Based On Fresnel Aperture
Dexing Liu; Jiaxin Shi; Yunkui Zhang; Ming Cai; Qingchen Niu; Guanhao Cui; Jun Gou; Jun Wang
University of Electronic Science and Technology of China, China

In this paper, the fringe phase scanning method based on Moire fringe is used to reconstruct the phase information of the target object. And we developed the two algorithms which are named as primary reconstruction and secondary reconstruction for different requirements. Combined with image enhancement technology, we can realize the lensless infrared imaging. This method is also beneficial to the miniaturization and integration of infrared focal plane detectors.

Tu-Po2-15
Low-pump Irradiance To Modulate THz Waves Driven By Photo-generated Carriers In An InAs Slab
Eduardo Alvear¹; Stephane Blin²; Philippe Nouvel²; Fernando Gonzalez-Posada²; Rafik Smaali³; Roland Teissier²; Alexei Baranov²; Thierry Taliercio²; Emmanuel Centeno^3
1Univ. Clermont Auvergne, France; ²IES, France; ³Univ. Clermont Auvergne, France

We theoretically and experimentally study the THz electromagnetic properties of an undoped-InAs slab whose permittivity is optically modified by a photo-generation process. The modulation of the permittivity is calculated by solving the ambipolar rate equation for the free carriers. Experiment results demonstrate that InAs is a promising semiconductor to manufacture fast and efficiently on-chip THz components. We show a high modulation of the THz transmission up to 100% from 0.75 to 1.1THz at very low pump fluence in the continuous wave regime. We also demonstrate a high-speed transmission modulation rate up to the MHz range with a modulated pump.

Tu-Po2-16
High Speed Antenna Enhanced Mid-infrared Quantum Cascade Detector
Gregory Quinchard¹; Alexandre Larrue¹; Alexandre Delga¹; Michel Garcia¹; Colin Mismer¹; Virginie Trinité¹; Axel Evirgen¹; Michael Hakl²; Jean-François Lampin²; Emilien Peytavit²; Stefano Barbieri^2
1III-VLab, France; ²IEMN, France

We demonstrate a λ =10.3 µm Quantum Cascade Detector embedded in a subwavelength optical patch antenna cavity. In this structure, the responsivity is enhanced by the microcavity effect and the dark current is reduced thanks to the antenna effect. The system is used as photo-mixer in a coherent photodetection scheme. It opens the way for high sensitivity and high-speed operation and brings new perspectives for room-temperature photodetection.

Tu-Po2-17
TeraHertz Generation in Semiconductor Microcavities
Hadrien Vergnet¹; Simon Huppert¹; Robson Ferreira¹; Aristide Lemaître²; Jacqueline Bloch²; Sukhdeep Dhillon¹; Emmanuel Baudin¹; Jérôme Tignon^1
1Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Universit, France; ²Centre de Nanosciences et de Nanotechnologies (C2N), CNRS - Université Paris-Sud / Paris-Saclay, France

We explore the potential of engineered exciton-polaritons in monolithic microcavities as compact and tunable THz emitters, by simultaneous THz and NIR spectroscopy

Tu-Po2-18
Numerical Study Of CO Laser Down-conversion In ZnGeP2 Crystal to THz Range
Igor Kinyaevskiy¹; Andrey Ionin¹; Yury Klimachev¹; Yury Andreev^2
1P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Russian Federation; ²Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of Russian Academy, Russian Federation

Difference frequency generation of rotational-vibrational lines of nonselective CO laser in ZnGeP2 crystal was numerically studied. It was shown that the difference frequency spectrum can be tuned at least in the wavelength range of 70--1300 ÃfŽÃ,¼m. The conversion efficiency can be up to 10-2%.

Tu-Po2-19
Room Temperature Silicon Detector For IR Range Coated With Ag2S Quantum Dots
Ivan Tretyakov¹; Alexander Shurakov¹; Alexey Perepelitsa¹; Natalya Kaurova¹; Tatyana Zilberley²; Sergey Ryabchun¹; Mikhail Smirnov³; Oleg Ovchinnikov³; Gregory Goltsman^1
1MSPU, Russian Federation; ²Moscow Institute of Physics and technology, Russian Federation; ³VSU, Russian Federation

For decades silicon has been the chief technological semiconducting material of modern microelectronics and has had a strong influence on all aspects of society. Applications of Si-based optoelectronic devices are limited to the visible and near infrared ranges. For photons with energy less than 1.12 eV silicon is almost transparent. The expansion of the Si absorption to shorter wavelengths of the infrared range is of considerable interest to optoelectronic applications. By creating impurity states in Si it is possible to cause sub-band gap photon absorption. Here, we present an elegant and effective technology of extending the photoresponse of towards the IR range. Our approach is based on the use of Ag2S quantum dots (QDs) planted on the surface of Si to create impurity states in Si band gap. The specific sensitivity of the room temperature zero-bias Si_Ag2S detector is 1011 cmâ^sHzW-1 at 1.55μm. Given the variety of available QDs and

Tu-Po2-20
Polarization Control Of Terahertz Spintronic Emitter Combined With Liquid Crystal By The External Magnetic And Electric Field
Makoto Nakajima¹; Hongsong Qiu¹; Lei Wang²; Zhixiong Shen³; Kosaku Kato¹; Yohei Koike¹; Masashi Yoshimura¹; Wei Hu³; Yanqing Lu^3
1Osaka University, Japan; ²Nanjing University Post and Telecommunications, China; ³Nanjing University, China

We demonstrate a polarization-tunable terahertz emitter that integrates a ferromagnetic heterostructure and large birefringence liquid crystals by the external magnetic and electric field. The direction of the magnetic field can control the emitted THz wave from linear to circular polarization. The phase retardation in liquid crystal layer between ordinary and extraordinary directions is continuously adjustable by the low-voltage electric field.

Tu-Po2-21
Terahertz Pulse Emission From GaInAsBi
Ričardas Norkus; Sandra Stanionytė; Andzej Urbanowicz; Andrius Bičiūnas; Vaidas Pačebutas; Arūnas Krotkus
State research institute Center for Physical Sciences and Technology, Lithuania

The quaternary GaInAsBi alloy epitaxial layers were grown on InP substrates with 6% Bi. It was found that thick layers are strained and has short of the order of few picoseconds carrier lifetimes. The THz emission was investigated using GaInAsBi layer as an unbiased surface emitter and as a substrate for photoconductive antenna. It was observed that fabricated THz emitters were sensitive to the optical pulses with the wavelengths longer than 2 µm. The demonstrated spectral characteristics of THz pulses obtained when using Er-doped fiber laser for the photoexcitation were comparable with those observed in other emitters used for THz-TDS systems

Tu-Po2-22
Synchronous Pumping Terahertz Parametric Oscillator Driven By Amplified Picosecond Mode-locked Laser
Tomohiro Naganawa¹; Heishun Zen²; Toshiteru Kii²; Hideaki Ohgaki^2
1Graduate School of Energy Science, Kyoto University, Japan; ²Institute of Advanced Energy, Kyoto University, Japan

Terahertz parametric oscillator (TPO) is one of the attractive ways to generate THz waves. However this scheme has big problem because of large loss and low conversion efficiency when it is driven by a nano-second pulsed laser. In this study, we propose a novel high-conversion-efficiency TPO, which is called as synchronous pumping Terahertz parametric oscillator (sp-TPO). It uses amplified picosecond mode-locked laser pulses as a pump beam. Design and construction of the device was completed, and the first test will be performed soon. The results will be also presented at the conference.

Tu-Po2-23
+16 DBm High Power And High Linearity Integrated Photoreceiver For W-band Fiber Wireless Communication Applications
Toshimasa Umezawa¹; Atsushi Kanno¹; Atsushi Matsumoto¹; Naokatsu Yamamoto¹; Tetsuya Kawanishi^2
1National Institute of Information and Communications Technology, Japan; ²Waseda University, Japan

We designed and fabricated an 80 GHz range high-power integrated photoreceiver operated using a zero-bias operational broadband uni-traveling carrier photodetector and a high-gain narrow-band amplifier. The results showed that by applying only a single power supply to the amplifier, the integrated photoreceiver could exhibit a higher power output at 1 dB compression (P1dB), i.e., over +16 dBm, and a 3 dB bandwidth of 6.5 GHz at 83 GHz.

Tu-Po2-24
High Efficient Broadband Terahertz Radiation Generated By Photoconductive Antenna Array
Wei Shi; Lei Hou; Cheng Ma; Lei Yang; Shaoqiang Wang; Chengang Dong; Hong Liu
Xi'an University of Technology, China

Coherent combination of radiations from a set of independent sources is an efficient way to obtain high power terahertz (THz) radiation. In this work, we designed and fabricated an antenna array, the THz radiations with opposite phase caused by the reverse bias electrical field existed in the conventional photoconductive antenna arrays was totally eliminated, and the synchronization of THz pulses was realized by precisely adjusting their optical paths. By these designs, we demonstrated, for the first time, the THz pulses with the combination efficiency of near 100% from photoconductive antenna array have been achieved.

Tu-Po2-25
Nonuniformity Study For Silicon-based BIB Terahertz Detectors
Xiaodong Wang; Yulu Chen; Bingbing Wang; Chuansheng Zhang; Haoxing Zhang
The 50th Research Institute of China Electronics Technology Group Corporation, China

In this work, Silicon-based BIB array detector has been fabricated. It is demonstrated that the minimum nonuniformity of 7.6% can be achieved. Additionally, the nonuniformities at the low bias are fundamentally less than those at the high bias, which can be attributed to the increased device temperature caused by the self-heating effect of the chip at the high bias. It can be deduced that the nonuniformity of dark current density will be out of control if the anode bias is larger than 3V due to the occurrence of avalanche randomness.

Tu-Po2-26
Fabrication Of Quarter THz Wavelength Resonant Cavity Using A Multiple spin Coating Process
Xing Zheng; Jingbin Wu; Yunkui Zhang; Ziji Liu; Zhiming Wu; Jun Gou; Tao Wang; Yadong Jiang
State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Scien, China

Due to the long terahertz (THz) wavelength, it remains a challenging problem to achieve THz wave absorption through building an effective optical resonant cavity for THz wave with THz focal plane arrays. In this paper, a multiple spin coating (MSC) process was developed for the first time to increase the height of the optical resonant cavity. Four resonant cavities with different heights were fabricated and their abilities to absorb THz waves were tested respectively. The tests suggested that the different THz bands were absorbed effectively by the micro-bridge structure using the proposed MSC process.

Tu-Po2-27
Simulation Of Terahertz Spectrum Generated By Noise-like Pulse
Yu Cheng Hong¹; Cheng Han Lin²; Hsiao Hua Wu²; Ci Ling Pan^2
1Institute of photonics technologies, Taiwan; ²Department of Physics, Taiwan

We simulate the generation of terahertz radiation by using a photoconductive antenna excited by noise-like pulses (NLPs). Our simulation results show that the bandwidth of THz spectrum generated by NLPs is narrower than by mode-locked pulses which is from the same laser system in the low-frequency region. However, the spectrum generated by NLPs exhibits additional components extended to the higher frequency, though the power is relatively low.

Tu-Po2-28
High Efficient THz Time Domain Spectroscopy Using Laser Chaos
Fumiyoshi Kuwashima¹; Takuya Shirao¹; Kazuyuki Iwao¹; Masahiko Tani²; Kazuyoshi Kurihara³; Kohji Yamamoto⁴; Osamu Morikawa⁵; Makoto Nakajima^6
1Fukui Univ. of Tech., Japan; ²Research Center for Development of Far-Infrared Region, University of Fukui, Japan; ³Fac. of Educ., Univ. of Fukui, Japan; ⁴Research Center for Development of Far-Infrared Region, University of Fukui, Japan; ⁵Chair of Liberal Arts, Japan Coast Guard Academy, Japan; ⁶Institute of Laser engineering, Osaka Univ., Japan

Stable and wide range THz waves are obtained from the chaotically oscillated multimode-laser diode excited photoconductive antennas. This system is chap system And. this THz wave is suitable for the spectroscopy. In this paper, it is applied to distinguish water and oil.

Tu-Po2-29
High Sensitivity Heterodyne Electro-Optic Sampling With 1.5-µM Laser Source
Hideaki Kitahara¹; Hiroyuki Kato¹; Masaki Shiihara¹; Akihiro Esaki¹; Kohji Yamamoto¹; Takashi Furuya¹; Elmer Estacio²; Micheal Bakunov³; Masahiko Tani^1
1University of Fukui, Japan; ²University of the Philippines Diliman, Philippines; ³University of Nizhny Novgorod, Russian Federation

A detection module for the heterodyne electro-optic sampling of terahertz pulses composed of a GaAs plate inserted into a tapered parallel plate waveguide has been designed and fabricated. The detector was installed into a standard terahertz time-domain spectrometer with a 1.5-µm femtosecond laser as a light source. The spectral bandwidth of 3.5 THz and dynamic range of 5 orders of magnitude were experimentally demonstrated, even with a photo-conductive antenna designed for 800-nm as an emitter.

Tu-Po2-30
Monolithic Mode-Locked Laser Diode For THz Communication
Alexandra Gerling¹; Kai Tybussek²; Quentin Gaimard³; Kamel Merghem³; Abderrahim Ramdane³; Martin Hofmann¹; Carsten Brenner¹; Jan Balzer^2
1Ruhr University Bochum, Germany; ²Universität Duisburg-Essen,Germany; ³CNRS Centre de Nanoscience et Nanotechnology, France

The need for higher data rates in wireless applications necessitates fast technological development. One option for advancement is the use of higher carrier frequencies, as this technique can incorporate previously established methods of data transfer such as modulation techniques. We show that generation and detection of multiple carrier frequencies in the THz range is possible using standard telecom equipment and a single mode-locked laser diode.

Tu-Po2-31
Generation Of Sub-100-kW Narrow-line Far-infrared Radiation From KTP Off-axis THz Parametric Oscillator Seeded By A Spectrally Filtered Stokes Pulse
Ming-Hsiung Wu; Wei-Che Tsai; Yu-Chung Chiu; Yen-Chieh Huang
National Tsing Hua University, Taiwan

We have reported narrow-line high-power far-infrared radiation with peak power up to 62 kW near 53 µm (~5.7 THz in units of frequency) from a pulse seeded OTPO using KTP. With 63% coupling efficiency of the silicon prism atop the KTP crystal, the measured 62-kW narrow-line far-infrared radiation in our pyrodetector correspond to 98-kW powers emitted from the KTP OTPO.

Tu-Po2-32
On-Chip Harmonically Mode-Locked Lasers In Generic Foundry As Frequency Multiplier For Optoelectronic Terahertz Generation
Mu-Chieh Lo; Robinson Guzmán; Guillermo Carpintero
Universidad Carlos III de Madrid, Spain

We experimentally demonstrated optoelectronic integrated circuits which generate selectable high-order harmonics from optical frequency combs to enable terahertz generation. These two-tone sources based on mode-locked lasers monolithically integrated with frequency multipliers are developed in an InP generic foundry approach.

Tu-Po2-33
Development Of High-speed, Patch-antenna Intersubband Photodetectors At 10.3um
Quyang Lin¹; Michael Hakl¹; Stefano Pirotta²; Raffaele Colombelli²; Wenjian Wan³; Hua Li³; J. C. Cao³; Jean-Francois Lampin¹; Emilien Peytavit¹; Stefano Barbieri^1
1Laboratoire IEMN - CNRS, France; ²Laboratoire C2N - CNRS, France; ³Key Laboratory of Terahertz Solid State Technology, Chinese Academy of Sciences, China

We present our work on the development of high-speed, GaAs-AlGaAs multi-quantum wells photodetectors at 10.3μm, based on two-dimensional arrays of patch-antenna resonators. First, the results of FDTD simulations will be presented that allowed to optimize the patch array geometry and fabricate a first generation of detectors with microwave coplanar access. Next, we will report on our initial results from dc optical characterization, namely reflectivity and photocurrent measurements.

Tu-Po2-34
The Gouy Phase Shift In Terahertz Time-domain Spectroscopy And Its Experimental Estimation, Modelling And Compensation
Pierre Kolejak¹; Kamil Postava¹; Martin Micica¹; Mathias Vanwolleghem²; Jaromir Pistora^1
1VSB-Technical University of Ostrava, Czech Republic; ²Université de Lille, CNRS UMR 8520, France

We propose techniques for compensation of the Gouy phase, which affects transmission time-domain spectroscopy measurements. It is proposed the method to analyze general influence of the Gouy phase. The model simulating the Gouy phase influence compared with measured data is also shown.

Tu-Po2-35
Single-shot Measurement Of THz Pulses With Sub-picosecond Resolution and Megahertz Acquisition Rates
Serge Bielawski¹; Christophe Szwaj¹; Clément Evain¹; Marc Le Parquier¹; Tianwei Jiang²; Cejo Lonappan²; Bahram Jalali^2
1PhLAM, LIlle University, France; ²Department of Electrical and Computer Engineering, University of California, United States

We present a method allowing THz pulses to be recorded in single-shot at tens of MHz repetition rates and long record lengths, using a combination of the time-stretch data acquisition and electro-optic sampling techniques

Tu-Po2-36
Application Of Mosaicity Induced Disorder Controlled Rare Earth Nickelate Thin Films As THz Transmission Modulator
Gulloo LAL PRAJAPATI¹; Sarmistha Das²; Dhanvir Singh Rana^1
1IISER Bhopal, India; ²Physics Department, University of California, United States

Here, we have studied mosaicity induced disorder (a unique type of disorder which is transferred from substrate template to film) controlled properties of rare earth nickelate thin films. While highly oriented film exhibits sharp metal to insulator transition (MIT) and Drude type of terahertz (THz) conductivity behavior, mosaic film exhibit much more subtle and broad transition and Drude-Smith type THz conductivity behavior. On the basis of such contrasting behavior, we propose application of these films as thermally controlled THz transmission modulator: oriented film as digital modulator while mosaic film as analog modulator.

Tu-Po2-37
Profile Control Of One-dimensional Terahertz Moth-eye Structure Fabricated By Femtosecond Laser Processing
Xi Yu; Jongsuck Bae; Shingo Ono
Nagoya Institute of Technology, Japan

To experimentally establishing the profile dependence of antireflective characteristic of moth-eye structure at THz frequencies, one-dimensional tapered moth-eye structures were fabricated on the surface of high-resistivity silicon substrate with different aspect ratio from 1.3 to 3.2 using femtosecond laser processing. A moth-eye structure consists of Klopfentein tapers with aspect ratio of 0.7 was also successfully fabricated by adjusted the scanning pattern while femtosecond laser processing. The antireflective characteristics of these samples were evaluated experimentally by a standard terahertz time domain spectroscopy and simulated by the High Frequency Electromagnetic Field Simulation.

Tu-Po2-38
Application Of Laser Generated Moth-eye Structure For A Periodic Terahertz-wave Generator
Xi Yu; Shingo Ono; Jongsuck Bae
Nagoya Institute of Technology, Japan

To improve the generation efficiency of terahertz wave from periodic terahertz-wave generator, femtosecond laser was employed to fabricated moth-eye structure on the reverse of the antenna substrate (LT-GaAs). The measurement performed by a THz-TDS system showed that The AR structured antennas had a 2.5-4.4 times improvement of the output. the output signals has an overall improvement at the region of 0.1-1.5 THz. At the frequency of 0.342 THz (calculated Ãfâ? Ã¢â,¬â"¢out), 283 THz, 226 THz (experimental Ãfâ? Ã¢â,¬â"¢out of generator without and with moth-eye, the improvement are 3 times, 2.5 times, and 4.4 times, respectively.

Tu-Po2-39
Electromagnetic-field Analysis Of Diagonal-feedhorn Antennas For Terahertz-frequency Quantum-cascade Laser Integration
Esam Zafar¹; Alexander Valavanis¹; Paul Dean¹; Edmund Linfield¹; Giles Davies¹; Yingjun Han¹; Olivier Auriacombe²; Thomas Rawlings²; Brian Ellison²; Nick Brewster²; Matthew Oldfield^2
1University of Leeds, United Kingdom; ²Science and Technology Facilities Council/RAL Space Department, United Kingdom

We present an electromagnetic-field analysis of a terahertz-frequency quantum-cascade laser (THz QCL) integrated with a mechanically micro-machined waveguide cavity and diagonal feedhorn. A hybrid finite-element/Fourier transform approach enables analysis of both the near-field and far-field regions and is shown to agree well with experimental observations. The far-field antenna patterns show enhancement of the beam profile when compared with an unmounted QCL, in terms of beam divergence and side-lobe suppression ratio. Furthermore, we demonstrate integration of the QCL with dual diagonal feedhorns, enabling simultaneous access to both facets of the QCL, underpinning future integration with a satellite-based receiver and frequency-stabilization subsystem

Tu-Po2-40
Open-Source Simulation Software For Quantum Cascade Lasers
Michael Riesch; Christian Jirauschek
Technical University of Munich, Germany

We review the state of the art in open-source simulation and optimization tools for quantum cascade lasers (QCLs) and present the mbsolve project, which is a tool for QCL dynamics simulations.

Tu-Po2-41
High Power THz Quantum Cascade Laser And Its Demonstration In High Resolution Holographic Imaging
Tao Jiang; Changle Shen; Zhiqiang Zhan; Ruijiao Zou; Xuemin Wang; Weidong Wu
Research Center of Laser Fusion CAEP, China

Fabrication of high power terahertz quantum cascade laser (THz QCL) based upon the resonant-phonon active region design and semi-insulating surface-plasmon waveguide with frequency at 4.4 THz and its demonstration in digital holographic imaging are presented. The maximum peak output power is 95mW at 10K in pulsed mode. The maximum working temperature is 80 K. Interestingly, by changing the injection current, the transverse mode of the laser can be switched between TM00 mode and TM01 mode. With such THz QCL as the light source, the lateral resolution of a home-built digital holographic imaging system can reach 80ÃZ¼m.

Tu-Po2-42
Towards A 4.75-THz Local Oscillator Based On A Terahertz Quantum-Cascade Laser With A Back-facet Mirror
Till Hagelschuer¹; Heiko Richter¹; Martin Wienold¹; Xiang Lü²; Benjamin Röben²; Lutz Schrottke²; Klaus Biermann²; Holger T. Grahn²; Heinz-Wilhelm Hübers^1
1German Aerospace Center (DLR), Germany; ²Paul-Drude Institut für Festkörperelektronik, Germany

We report on a compact terahertz (THz) source based on a quantum-cascade laser (QCL). The source is intended for a local oscillator in a THz heterodyne receiver for the detection of the fine structure line of neutral atomic oxygen (OI) at 4.7448 THz. The QCL which is mounted in a small mechanical cryocooler employs a GaAs/AlAs active-region heterostructure and a resonator with an additional back-facet mirror. This allows for low electrical pump powers of less than 1.2 W and high optical output powers of up to 8 mW. The whole setup weighs less than 4 kg. The application of such a system in a spaceborne mission appears to be feasible.

Tu-Po2-43
Optimization Of THz QCLs By Suppressing A Leakage Current Via High Energy States
Tsung-Tse Lin; Ke Wang; Li Wang; Hideki Hihayama
RIKEN, Japan

Terahertz quantum cascade lasers (THz QCLs) are theoretically analyzed based on the non-equilibrium Green's function (NEGF) method. Simulations reveal a carrier leakage channel from upper laser level to the first high energy state in the emitting double-well of the next period. This leakage channel is due to unintentional alignment of the two states, which is distinct from the thermally activated leakage channels. By tuning the energy of this high energy state, such leakage current is clearly suppressed.

Tu-Po2-44
The Material Growth, Device Fabrication And Application Of Terahertz Quantum Cascade Lasers
Weidong Wu; Xuemin Wang; Changle Shen; Tao Jiang; Zhiqiang Zhan
Research Center of Laser Fusion CAEP, China

This talk reviews our recent work on material growth, device fabrication and application of terahertz quantum cascade lasers (THz QCLs).

Tu-Po2-45
Advances In MOEMS-based External Cavity QCLs For Mid-IR Spectroscopy
Yuri Victorovich Flores¹; Marko Haertelt¹; Stefan Hugger¹; Lorenz Butschek¹; Christian Schilling¹; Andre Merten²; Markus Schwarzenberg²; Andre Dreyhaupt²; Jan Grahmann²; Marcel Rattunde¹; Ralf Ostendorf^1
1Fraunhofer Institute of Applied Solid State Physics, Germany; ²Fraunhofer Institute for Photonic Microsystems, Germany

We present miniaturized MOEMS-based external-cavity (EC)-QCLs: A non-resonant, versatile version for setting arbitrary emission wavelengths or wavelength trajectories as a function of time with drive frequencies up to a few tens of Hz and a fast, resonant variant for real time (millisecond resolution) measurements. Both versions are equipped with additional cavity length control for high-resolution mid-IR spectroscopy.

Tu-Po2-46
High Performance Continuous-wave InP-based 2.1 ?m Superluminescent Diode With InGaAsSb Quantum Well
Jinchuan Zhang
Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Science, People's Republic of China, China

Broadband spectrum electrically pumped InP-based superluminescent diodes (SLDs) in continuous-wave (CW) are reported. The optimized active region and high quality of quantum wells are guaranteed for controlling wavelength and acquiring large mode gain. All device spectrums are centered around 2.1 μm and the full width at half maximum (FWHM) of widest spectrum is 99 nm. After the optimization of waveguide structure for higher output power, the maximum CW output power is lifted up to 30 mW. This work is of great importance to pave the way for demonstrating compact and efficient light sources based on InP material systems.

Tu-Po2-47
Resonant Frequency Tuning Of Terahertz Plasmonic Structures Based On Solid Immersion Method
Toshio Sugaya¹; Xiangying Deng¹; Yukio Kawano^2
1Tokyo Institute of Technology, Japan; ²Laboratory for Future Interdisciplinary Research of Science and Technology, Tokyo Institute of Techn, Japan

We report on a technique for resonant frequency tuning and miniaturization of a terahertz (THz) plasmonic structure. By applying solid immersion method to a nonconcentric plasmonic structure, we achieved resonant frequency tuning of THz plasmon and size reduction by 1/3.41 simultaneously. These results potentially lead to high-resolution THz analysis for bio-medical examination and nano-materials characterization.

Tu-Po2-48
Comparison Of Metallic NW And Evaporated Contact For THz Detector Modules Based On An InGaAs Schottky Diode
Ahid S. Hajo; Oktay Yilmazoglu; Suwei Lu; Franko Küppers; Thomas Kussorow
Technische Universität Darmstadt, Germany

In this paper we report a new Terahertz (THz) Schottky detector module based on vertically contacted highly doped (1 x 1018 cm-3) indium gallium arsenide (InGaAs) by using a small diameter (100 nm) silver nanowire (NW) as air-bridge contact and a standard evaporated contact (SD). These Schottky diodes were placed on a silicon lens and integrated with a pre- amplifier on a printed circuit board (PCB).

Tu-Po2-49
Characterization Of Uncooled Ultra Low-NEP LSMO Bolometers At 3.39 Mm And In The MWIR And LWIR Bands
Bruno Guillet¹; Vanuza Marques Do Nascimento¹; Victor Pierron¹; Laurence Méchin¹; Florent Starecki²; Carolina Adamo³; Darrell Schlom^4
1GREYC - CNRS/ENSICAEN/Université de Caen Normandie, France; ²CIMAP - CNRS/ENSICAEN/CEA/Université de Caen Normandie, France; ³Cornell University, United States; ⁴Kavli Institute at Cornell for Nanoscale Science, United States

La0.7Sr0.3MnO3 (LSMO) uncooled suspended bolometers have been characterized at 3.39 Ã,µm (He-Ne laser) and with a blackbody source at different temperatures. These bolometers could achieve ultra low NEP values below 1 pWÃ,·Hz-1/2 with few microwatts power consumption at 300 K

Tu-Po2-50
A Gap Waveguide Fed Circular Polarization Antenna In The Millimeter- Wave Range
Dayan Pérez; Miguel Beruete; Iñigo Ederra
Public University of Navarra, Spain

In this paper a simple diamond-shaped slot antenna working in the millimeter-wave 5G band of 60 GHz, with circular polarization (CP), high radiation efficiency and broadband performance both in matching and axial ratio (AR) is presented. The antenna is implemented in Gap Waveguide (GW) technology, namely Ridge Gap Waveguide topology. The feeding system is a standard waveguide (WR-15) to RGW transition. The simulation results demonstrate a 14.52% reflection coefficient and AR bandwidth (|S11 < ?10 dB| and AR < 3dB) covering 59- 68 GHz (> 9 GHz) The maximum gain of the system is around 7 dB, with an efficiency close to 98%.

Tu-Po2-51
Investigation Of THz Tapered Parallel Plate Waveguide Integrated With A Metal Slit Array
Dejun Liu¹; Borwen You¹; Ja-Yu Lu²; Toshiaki Hattori^1
1University of Tsukuba, Japan; ²National Cheng Kung University, Taiwan

A metal slit array in a tapered parallel plate waveguide (TPPWG) is experimentally and numerically demonstrated. The metal slit array is embedded in the center of air gaps in tapered regions, realizing multiple narrow Bragg resonances. TPPWG not only enhances the Bragg resonances but also reduces the number of non-Bragg resonances. The induced standing waves at 0.3 THz exhibits enhanced localized field with four antinodes, which originates from the interference between two THz waves divided by the metal slit array.

Tu-Po2-52
Design Of A Compact Cylindrical Micro-lens For Efficient Out-coupling And Collimation Of THz Radiation From A Photoconductive Antenna
Thomas Søndergaard; Christian Sørensen; Esben Skovsen
Aalborg University, Department of Materials and Production, Denmark

A compact cylindrical micro-lens is designed for efficient out-coupling and collimation of THz radiation from a photoconductive THz antenna placed on the backside of a semiconductor substrate. The full radiation pattern of the 3D lens-antenna system is calculated rigorously by using the Green's Function Volume Integral Equation Method in a form that exploits cylindrical symmetry. The lens is designed for an optimum amount of radiation emitted in a useful range of directions relative to the total emission taking into account the Purcell effect and radiation trapped inside the semiconductor substrate

Tu-Po2-53
Tunable Optical Frequency Shifter For Terahertz Communicaiton System
Wei Jiang¹; Shanghong Zhao²; Qinggui Tan¹; Xiaojun Li¹; Zhongbo Zhu^1
1National Key Laboratory of Science and Technology on Space Microwave, China; ²Air Force Engineering University, China

In this paper, a tunable optical frequency shifter for Terahertz (THz) communication system is proposed and demonstrated. The scheme is based on frequency multiplication operation using dual-parallel DPMZM (dual-parallel Mach-Zehnder modulator) and Mach-Zehnder interferometer (MZI). By optimizing the sub-modulators of DPMZMs, the optical carrier suppressed single-side-band signal (SSB-OCS) with adjustable order can be used for tunable optical frequency shifter, and the MZI further suppresses high order intermodulation components. The simulated results show the suppression ratio is above 30 dB, and the maximum range of optical frequency shift is over 150 GHz. The experimental test suppression ratio is over 24 dB.

Tu-Po2-54
Study Of Microstrip-Based Terahertz Phase Shifter Using Liquid Crystal
Yuki Takeda¹; Withawat Withayachumnanku²; Yasuaki Monnai^1
1Keio University, Japan; ²The University of Adelaide, Australia

We propose a microstrip-based terahertz phase shifter using liquid crystal. Voltage-controlled phase shift can be induced by incorporating liquid crystal into the dielectric substrate of the microstrip line (MSL) to cause the refractive index change. DC bias lines running in parallel to the MSL are designed to introduce minimum RF interference. Preliminary experimental results show the proof of concept of the approach.

Tu-Po2-55
Rapid Prototyping Of Simple Optical Elements For The Terahertz Domain
Christian Sørensen¹; Esben Skovsen^2
1Aalborg University, Department of Materials and Production, Denmark; ²Aalborg University, Denmark

This work shows practical details of methodologies for conventional milling of arbitrary spherical lenses from high-density polyethylene as well as the production and polishing of off-axis parabolic mirrors using fused filament fabrication 3D printing. The techniques allow for low-volume, low-cost and fast prototyping of large optical elements for prototype setups.

Tu-Po2-56
THz Gratings Produced By Laser Cutting
Jan Ornik; Yingzhi Zhang; Maximilian Schneider; Mehdi Taherkhani; Hakan Alaboz; Martin Koch
Philipps-Universität Marburg, Germany

We produced terahertz gratings from aluminum and PVC foil by laser cutting. The performance of the produced gratings was simulated and found to be in good agreement with the experimental characterization.

Tu-Po2-57
A Quasi-optical Transmission Line For The ECR Ion Source
jianwei liu¹; junwei guo²; xinjian niu¹; yinghui liu¹; hui wang¹; guo guo¹; Safi Ullah¹; Abdur Rauf¹; xu sun^1
1University of Electronic Science and Technology of China, China; ²Institute of Modern Physics (IMP), Chinese Academy of Science, China

A compact, efficient, 45GHz/20KW quasi-optical transmission line consisting five quasi-optical mirrors for the ECR ion source, which constructed by the Institute of Modern Physics(IMP), Chinese Academy of Science has been proposed. A computer code for vector analysis of the electromagnetic fields in mirror systems has been developed in terms of the vector diffraction theory. Based on Stratton-Chu formula and mirror optimization program, the structure of the five quasi-optical mirrors has been obtained. The simulation results show that the power transmission efficiency from the output of the Matching Optical Unit( MOU) to the vacuum widow which connected with superconducting ECR ion source is 93.53%. The experimental results indicate that a good agreement between measurement and theoretical prediction is obtained.

Tu-Po2-58
Development Of The Planar AlGaN/GaN Bow-tie Diodes For Terahertz Detection
Justinas Jorudas; Justina Malakauskaitė; Liudvikas Subačius; Vytautas Janonis; Vytautas Jakstas; Vitalij Kovalevskij; Irmantas Kasalynas
Center for Physical Sciences and Technology, Lithuania

Completely planar bow-tie (BT) diodes for terahertz (THz) detection were developed on AlGaN/GaN high electron mobility transistor (HEMT) structures employing a shallow ion-implantation for electric isolation. Heating in a two dimensional electron gas (2DEG) layer in the apex zone of geometrically shaped semiconductor was used for THz detection. The diodes were developed with various apex widths varying from 17 µ to 500 nm. The responsivity of the sensor was found to be increasing non-linearly with the decrease of the apex width. In addition, detected signal dependence on frequency was observed with a maximum sensor response at about 150 GHz defined by a THz antenna coupling efficiency and not 2DEG heating effects. These results highlight a potential of the planar AlGaN/GaN BT diodes for the usage upper THz frequency range.

Tu-Po2-59
Concept Of A Prism Spectrograph For Infrared Linear Array Detectors
Ulrich Schade¹; Eglof Ritter²; Ljiljana Puskar¹; Paul Dumas^3
1HZB, Germany; ²HUB, Germany; ³SOLEIL Synchrotron, France

We discuss the concept of an IR spectrograph suitable for linear array detection. The dispersive element of the spectrograph is based on an arrangement of commercially available low-cost prisms. The dispersion is such that the whole spectral bandwidth of interest is distributed along the linear array of detector pixels in such a way to achieve an optimum for the spectral resolution. The concept is exemplarily shown for the design of a spectrograph working in the range between 5000 and 2500 wavenumbers spread onto a linear 128-pixel array detector.

Tu-Po2-60
A Low-Profile Sub-Terahertz Transmit-Array Antenna With High Gain Enhancement
Zhongbo Zhu¹; Weidong Hu²; Xianqi Lin³; Xiaojun Li^1
1The National Key Lab. of Sience and Technology on Space Microwave, China; ²Beijing Institute of Technology, China; ³University of Electronic Science and Technology of China, China

A compact transmit-array (TA) antenna with reduced profile and improved radiation gain is proposed in this paper. The proposed transmitting surface, with a thickness of 0.127 mm (0.042 ?0 @105 GHz), is employed here to adjust the phase distribution across the aperture of a shortened feed horn. The full TA prototype is fabricated and measured. A 3-dB gain bandwidth of 9.52%, from 100 GHz to 110 GHz, is achieved. The measured maximum gain at 105 GHz is 22.76 dBi, which gets an 8-dB enhancement with respect to the primary feed, without expanding the radiation aperture size. This method considerably reduces the complexity of TA and achieves a much more compact structure.

Tu-Po2-61
Detection Performance Of LT-GaAs-on-Silicon Bowtie Photoconductive Antenna Prototype
Jessica Afalla¹; Alexander De Los Reyes²; Maria Angela Faustino²; Victor DC Vistro²; Hannah Bardolaza²; Gerald Angelo Catindig²; Karl Cedric Gonzales²; Elizabeth Ann Prieto²; Joselito Muldera³; Valynn Mag-usara⁴; Neil Irvin Cabello²; Vernalyn Copa²; John Paul Ferrolino²; Garik Torosyan⁵; Takashi Furuya⁴; Hideaki Kitahara⁴; Armando Somintac²; Arnel Salvador²; Masahiko Tani⁴; Elmer Estacio^2
1University of Fukui, Japan; ²University of the Philippines Diliman, Philippines; ³de la Salle University, Philippines; ⁴University of Fukui, Japan; ⁵Photonic Center Kaiserslautern, Germany

We report on the detection characteristics of two bowtie photoconductive antennas which were fabricated on low temperature grown GaAs grown on Silicon substrates. The bowtie structure has a 10-µm antenna gap. The two samples have unique growth recipes, and were epitaxial grown on differently oriented substrates. The sample grown on a Si (100) substrate with a 4° tilt towards the (110) direction, has a longer carrier lifetime (24 ps) and higher detection intensity as a photoconductive antenna. The sample grown on a Si (100) substrate has a carrier lifetime of 13 ps. Its detection intensity was found to be lower, but its bandwidth slightly wider.

Tu-Po2-62
Combined UTC-PD Integrated On-chip THz Near Field Microscopy With Coupled Planar Goubau Lines
Tahsin Akalin¹; Abdallah Chahadih²; Abbas Ghaddar²; Ibrahim Türer^3
1Lille University, France; ²Lebanese University, Faculty of science, Lebanon; ³Airbus Defence and Space, Germany

In most of the cases for terahertz near field microscopy, a free space propagating electromagnetic wave interacts with a small tip placed above the sample. In our original approach, we use a guided way to bring the terahertz wave and to improve the interaction efficiency with the sample. The idea is to take benefit of the confinement around a Planar Goubau Line (PGL). We have fabricated a planar system with an integrated Uni-Travelling-Carrier Photodiode (UTC-PD) as a broadband source. The system can be used to map continuously at discrete frequencies the sample in a wide frequency range.

Tu-Po2-63
Characterization Of Smooth Dielectric Samples With Highly Focused Gaussian Beams In A Scatterometer
Michal Mrnka¹; Per Heighwood Nielsen²; Tonny Rubæk²; Cecilia Cappellin²; Roger Appleby³; Elena Saenz^1
1ESA-ESTEC, Netherlands; ²TICRA, TICRA, Denmark; ³Roger Appleby MMW Consulting Ltd., United Kingdom

This paper describes a numerical validation of the transmission coefficient of a smooth dielectric sample recently measured at ESA-ESTEC during the integration testing of a scatterometer operating in 50-750 GHz frequency range. The aim of the paper is to compare the experimental results of a calibrated measurement with a numerical model in GRASP and describe a numerical method for extracting material parameters.

Tu-Po2-64
Terahertz Near-Field Imaging Using Batch Fabricated Cantilevers With 70 Micrometers Long Tips
Benjamin Walter¹; Estelle Mairiaux¹; Dominique Vignaud²; Sophie Eliet²; Jean-Francois Lampin²; Marc Faucher^2
1Vmicro SAS, France; ²Univ. Lille, CNRS, Centrale Lille, ISEN, Univ. Valenciennes, France

Batch fabricated atomic force microscopy cantilevers with tip longer than 70µm are reported. They are designed to increase terahertz focusing in scattering optical near field imaging. Terahertz SNOM imaging of sub-100nm features on a graphene sample is presented.

Tu-Po2-65
Terahertz Field Enhancement By Bull's Eye Antenna For Force-detected Electron Paramagnetic Resonance Measurements
Ren Fujioka¹; Hideyuki Takahashi²; Kengo Sugahara³; Eiji Ohmichi¹; Hitoshi Ohta^2
1Graduate School of Science, Kobe University, Japan; ²Molecular Photoscience Research Center, Kobe University, Japan; ³School of Science and Engineering, Kindai University, Japan

We designed bull's eye antenna structure working at THz frequencies for use in force-detected EPR measurement, and numerically confirmed that the oscillating magnetic field B1 was focused into the subwavelemgth scale at the aperture with an enhancement by one order.

Tu-Po2-66
Passive Millimeter-wave Microscopy Of Aqueous Protein Solutions at Low Temperatures
Tatsuo Nozokido¹; Yuya Takakura¹; Akio Kishigami^2
1University of Toyama, Japan; ²Gifu Women's University, Japan

Thermal radiation emitted from aqueous solutions of bovine serum albumin (BSA), which is a serum albumin protein derived from cows, was measured and analyzed by passive millimeter-wave microscopy at temperatures below the freezing point of water. The thermal radiation emitted from BSA aqueous solutions with different concentrations was measured at 50 GHz and temperatures ranging from 130 K to 260 K. Two different conformational states of the BSA were observed. The emissivities of the BSA solutions were successfully determined from the measured results.

Tu-Po2-67
Compressed Sensing Image Reconstruction For Millimeter-wave Near-field Scanning Microscopy Using A Metal Slit Probe
Tatsuo Nozokido¹; Hiroki Okano¹; Hiroyuki Kudo^2
1University of Toyama, Japan; ²University of Tsukuba, Japan

We report on the use of a compressed sensing technique for two-dimensional image reconstruction in millimeter-wave near-field scanning microscopy that enables the measurement time required to acquire the projection data sets to be reduced. Experiments performed at 60 GHz to image the electrical response anisotropy of the sample using compressed sensing image reconstruction show that just 1/8th of the full scan data needs to be measured to allow perfect image reconstruction.

Tu-Po2-68
Propagation characteristics of high-throughput terajet beam and its super Resolution THz imaging
Qingshan Qu¹; Bin Cui¹; Zhenwei Zhang²; Yuping Yang¹; Zhichao Yang^1
1Minzu University of China, China; ²Capital Normal University, China

Broad-bandwidth spectral analysis is one of important advantages of terahertz (THz) imaging technology, while low spatial resolution restricts its further applications. In contrast to the contradiction between the high-resolution and the low-throughput as well as narrow-bandwidth in the existing THz near-field imaging technologies, a high-resolution, high- throughput and broad-bandwidth terahertz imaging method is proposed in this work based on the terajet effect produced by a dielectric semi-sphere with appropriate refractive index. The terajet beam can break through the restriction of the diffraction limit on the spatial resolution of the microscopic system without losing the energy and spectral width.

Tu-Po2-69
TeraFET Multi-pixel THz Array For A Confocal Imaging System
Dovilė Čibiraitė¹; Min Wan²; Alvydas Lisauskas³; Adam Rämer⁴; Sergey Chevtchenko⁴; Wolfgang Heinrich⁴; Hartmut G. Roskos¹; John T. Sheridan²; Viktor Krozer¹; Viktor Krozer^4
1Goethe University Frankfurt, Germany; ²University College Dublin, Ireland; ³Vilnius University, Lithuania; ⁴Ferdinand-Braun-Institut, Germany

We present a THz detector based on AlGaN/GaN HEMT technology implemented for a multi-pixel array and tested in a confocal THz imaging system. The multi-pixel array shows good homogeneity where the ratio between the most and the least sensitive pixels is less than two times. The detector has been tested in a confocal system at 300 GHz and the pictures show a good resolution.

Tu-Po2-70
Fabrication And Characterization Of Frequency Selective Terahertz Focal Plane Array And Camera
Hassane Oulachgar; Jacques-Edmond Paultre; Marc Terroux; Francis Provençal; Bruno Fisette; Hélène Spisser; François Berthiaume; Alex Paquet; Michel Doucet; Michel Jacob; Linda Marchese; Francis Généreux; Paul Grenier; Christine Alain; Alain Bergeron
National Optics Institute, Canada

A high performance frequency selective focal plane array (FPA) detector has been developed at INO. The detector array was fabricated using a CMOS compatible microfabrication process. The FPA consists of a 384x288 pixel array, with optimal detection frequency at 515 GHz. The radiometric performance of the detector, at this frequency, was improved by more than five-fold compared to previously reported frequency selective terahertz detector [2].

Tu-Po2-71
Modeling And Simulation Of Dielectric Whispering Gallery Mode Sensor Using Finite Element Method At THz Frequency
Himanshu Gohil¹; Anushree Singh¹; Cijy Mathai²; Niraj Joshi³; Shriganesh Prabhu^1
1Tata Institute of Fundamental Research, India; ²Indian Institute of Technology - Bombay, India; ³SCEM, Mangalore, India

The design and optimization of Whispering Gallery Mode Resonator (WGMR) sensors in the THz regime can be modelled using Finite Element Analysis. In this paper, we have modelled and simulated a rectangular cross section ring WGMR and its response for the biomolecule analyte 'BSA' (Bovine Serum Albumin) at the THz frequencies. We design our resonator model for working frequency of around 0.161 THz using dielectric core with Refractive Index of 1.473, corresponding to HDPE and use the experimentally obtained refractive index of analyte. The simulation results after placing the analyte near the resonator evokes a response in the form of a characteristic peak frequency shift of 80 MHz and line broadening (~3x FWHM). These theoretical results can be used to study and obtain parameters to fabricate optimized devices which can yield results for sensing unlabeled analytes with low concentration and high specificity.

Tu-Po2-72
A GO/FO Tool For Analyzing Quasi-Optical Systems In Reception
Huasheng Zhang; Shahab Oddin Dabironezare; Giorgio Carluccio; Andrea Neto; Nuria Llombart
Delft University of Technology, Netherlands

In this work, a free accessible MATLAB interface is presented to analyze antenna-coupled Quasi-Optical (QO) systems in reception. This goal is achieved by using Fourier Optics (FO) and Geometrical Optics (GO) based methods. Specifically, the FO method represents the field focalized by a QO component on its focal plane as a plane wave spectrum when the component is illuminated by an incident field. This spectrum is related to the field scattered by the QO component which is calculated here using a GO method. By using this spectrum, the tool estimates the power received by an antenna placed at the focal plane of the QO component. Moreover, the performance in reception is evaluated.

Tu-Po2-73
Terahertz Imaging Based On Coherent Detection Of The Fourier-Space Spectrum
Hui Yuan¹; Daniel Voß¹; Min Wan²; Alvydas Lisauskas³; Hartmut G. Roskos¹; John T. Sheridan^2
1Physikalisches Institut/Johann Wolfgang Goethe-Universität, Germany; ²School of Electrical & Electronic Engineering / University College Dublin, Ireland; ³Institute of Applied Electrodynamics & Telecommunications / Vilnius Univ., Germany

A novel continuous-wave THz imaging system based on the coherent recording of the Fourier space spectrum (FSS) with heterodyne detection is described. The system consists of two 300-GHz electrical multiplier-chain sources with a slight frequency offset, and a single narrow-band TeraFET detector working in raster-scanning mode. The complex-valued FSS is recorded in either the focal-plane or in the free space of the optical system in focusing and non-focusing mode, respectively. Two- and three-dimensional (2D and 3D) images are reconstructed numerically with an inverse Fourier transform algorithm. With a 80×80-mm2 detection area and 1-mm2 sampling steps, 1-mm resolution and 76.2×76.2-mm2 image area are achieved.

Tu-Po2-74
Tunable Filter Design For IR Hyperspectral Imaging
Justine Champagne; Samuel Dupont; Joseph Gazalet; Jean-Claude Kastelik
IEMN, France

The use of wide-angle Acousto-Optic Tunable Filter (AOTF) for hyperspectral imaging is considered: the diffraction efficiency is calculated around a usual diffraction plane for two degrees of freedom (azimuthal and transverse angle). The efficiency evolution is also examined over a wide wavelength band. The diffraction efficiency is determined as a function of the incident angles and the results are commented.

Tu-Po2-75
3D Inspection Of Fiber-Reinforced Thermoplastics At THz Frequencies
Matthias Kahl; Jan Boecking; Bernd Engel; Peter Haring Bolívar
University of Siegen, Germany

Utilizing composite materials instead of metals allows to reduce weight while maintaining mechanical strength. Fiber-Reinforced Thermoplastics (FRT) have very competitive mechanical properties and additionally offer the capability for mass production, which makes the material particularly attractive in the automotive and aircraft sectors. Typical defects in FRT are dominated by fiber shifts and cracks. We show that 3D THz imaging using a FMCW approach can resolve such defects and is therefore a suitable tool for nondestructive testing applications, specifically for the quality control in FRT mass production.

Tu-Po2-76
A Convolutional Neural Network For The Non-destructive Testing Of 3Dprinted Samples
Mostafa Elsaadouny; Jan Barowski; Ilona Rolfes
Ruhr University Bochum, Germany

The three dimensional printing is a very important technology that participates in many applications. In this paper we present an approach for the Non-Destructive Testing (NDT) of the three dimensional printed objects. This methodology solves the image classification problem by using the Neural Networks (NN). The network has been trained by large data matrix which contains information about the mean, the variance and the pixel intensity of the input. The proposed solution has been used for testing different data sets for monitoring the performance under different scenarios, and the obtained results show high degree of accuracy regarding defects detection.

Tu-Po2-77
High Responsivity And Low NEP Of Room-Temperature Terahertz Antenna-Coupled Microbolometers With Meander Titanium Thermistor
Norihisa Hiromoto¹; Amit Banerjee²; Durgadevi Elamaran¹; Makoto Aoki³; Catur Apriono⁴; Hiroaki Satoh¹; Erik Bruendermann⁵; Eko Rahardjo⁴; Hiroshi Inokawa^1
1Shizuoka University, Japan; ²National University of Singapore, Singapore; ³National Institute of Information and Communications Technology (NICT), Japan; ⁴Universitas Indonesia, Indonesia; ⁵Karlsruhe Institute of Technology (KIT), Germany

In order to realize room-temperature terahertz (THz) detectors with high-detectivity, we have studied room- temperature THz antenna-coupled bolometers with titanium (Ti) meander-line thermistor fabricated on a high-resistivity silicon (Si) substrate by MEMS structures. In this paper, we report the spectrum of responsivity which spreads in the range of 0.1 THz width around 1 THz and it has high-responsivity bands with the orders of 1000 V/W. Thanks to the high responsivity and low noise of the metal thermistor, we have achieved good noise-equivalent power (NEP) of the order of 10^-11 W/Hz^1/2 and response speed of 5 kHz for the room-temperature antenna-coupled bolometers with Ti meander thermistor 0.1 µm-wide and 90 µm-long.

Tu-Po2-78
Incoherent Power Combining Of THz Source Arrays
Robin Zatta¹; Ritesh Jain²; Daniel Headland³; Ullrich Pfeiffer^1
1Institute for high frequency & communication technology, Germany; ²Bergische Universität Wuppertal, Germany; ³Graduate School of Engeneering Science of Osaka University, Japan

In this paper, we investigate the multi-chip scaling of a previously developed incoherent 4x4-pixel 0.53-THz 1- mW source array, implemented in a 0.13-um SiGe BiCMOS technology. A standalone module under-samples the illumination space due to a large pixel pitch given by the implemented triple-push oscillator topology coupled with narrow pixel beams. Therefore, we present the concept of super-array configurations by arranging multiple source arrays, achieving an increased fill factor, increased radiated power, and wider illumination aperture. Moreover, such super-array configurations can help to reduce the influence of spurious reflections at THz frequencies by providing a diffused radiation. For a 2x1 super-array, the 10-dB fill factor increased from 10.9 to 61.8% while maintaining the illumination aperture; and the net radiated power doubled to 2 mW (3 dBm). For a 2x2 super-array, the illumination aperture quadrupled; the radiated power and the 10-dB fill factor at 0.53 THz were 4 mW (6 dBm).

Tu-Po2-79
Kernel Size Characterization For Deep Learning Terahertz Tomography
Yi-Chun Hung¹; Shang-Hua Yang^2
1National Tsing-Hua University, Taiwan; ²Department of Electrical Engineering, National Tsing Hua University, Taiwan

We present supervised terahertz deep learning models for high-precision terahertz tomography. To investigate the performance of terahertz deep learning models, comprehensive characterization of kernel size in first convolution layers is further studied. By utilizing the length of beam diameter, the optimized kernel size can be designed to deliver the much spatially accurate images, which achieves 2.5% on mean square error (MSE) , 46.8% improvement on MSE than other kernel size.

Tu-Po2-80
340 GHz And 250 GHz Schottky Solid-state Heterodyne Receiver Arrays For Passive Imaging Systems
Yue He¹; Li Wei Hou²; Yao ling Tian¹; Kun Huang¹; Jun Jiang^1
1Microsystem and Terahertz Research Center, China; ²The 50th research institute of china electronics technology group corporation, China

Two four-pixel receiver arrays for operation in 340 and 250 GHz passive imaging system are presented. The millimeter-wave front-end components and THz mixer are achieved by the planar GaAs Schottky-barrier varactor to obtain good performance in room temperature while lowering the cost and difficulty compared to integrated circuit. The discrete 340GHz and 250GHz mixers have the lowest DSB noise temperature of 1020K and 900K respectively within the operation band . A broadband IF bandwidth, 20GHz, is adopted in passive imaging systems for increasing the received human body radiation power. Good detection performance and space resolution is still obtained for object distances 3-8m. Compared to the current sensors operated in cryogenic imaging system, the receiver array is a cheap and feasible method for personal security screening

Tu-Po2-81
Broadband Bendable Terahertz Camera For Built-in Infrastructure Sensor
Daichi Suzuki¹; Koji Ishibashi¹; Yukio Kawano^2
1RIKEN Center for Emergent Matter Science, Japan; ²Tokyo Institute of Technology, Japan

We present a broadband bendable THz camera, composed of a free-standing carbon nanotube film array, which is intended for an built-in infrastructure sensor. As advantages over conventional solid-state THz sensors, our bendable THz camera can be fabricated through simple and low-cost processes and can simplify optical/electrical measurement systems, which enables us to mount the sensor on objects regardless of their shapes, sizes, and locations. We demonstrate the use of our novel THz camera for real-time nondestructive imaging of industrial products, indicating possibilities of one of the powerful components such as built-in/wearable THz sensors for future imaging and remote sensing.

Tu-Po2-82
A Full-wave Analysis Of Lenses For THz Detectors Purposes
Pawel Kopyt¹; Bartlomiej Salski¹; Jerzy Cuper¹; Przemyslaw Zagrajek^2
1Warsaw University of Technology, Poland; ²Military University of Technology, Poland

In this work an analysis of power density inside various types of lenses is presented. Properties of structures commonly used in THz detectors have been verified using a full-wave EM simulations. Two alternative implementations of EM solvers have been considered. Possibility of replacing spherical-based structures with more sophisticated elliptical lenses were considered as well, showing similar properties

Tu-Po2-83
THz Super-Resolution Imaging With Parallel-Pixel Data Acquisition For Rapid Inspection Applications
Rungroj Jintamethasawat; Chayut Thanapirom; Patharakorn Rattanawan; Napat Cota; Natcha Cota; Chia Jia Yi; Kittipong Kasamsook
National Electronics and Computer Technology Center, Thailand

A multi-frame, super-resolution imaging algorithm for a THz array detector with parallel-pixel data acquisition is proposed to overcome both detector resolution limit and prolonged acquisition time. A correction scheme was also implemented to counteract a fixed-pattern noise caused by non-uniform pixel responsivity observed in our experimental results. The proposed technique aims to serve the demands for THz non-destructive testing (NDT) and quality control (QC) applications, which requires a rapid high-resolution THz imaging system.

Tu-Po2-84
A Terahertz Superconducting Single-Pixel Imaging System Using DMD
Yilong Zhang; Yuan Ren; Wei Miao; Hao Gao; Shengcai Shi
Purple Mountain Observatory, Chinese Academy of Sciences, China

We propose a terahertz superconducting single-pixel imaging system with a single hot electron bolometer (HEB) detector combined with a digital-mirror-device (DMD). With the DMD as a programmed coding reflector, the proposed imaging system could acquire coded measurement results of an imaged scene rapidly even with a single detector. Base on compressive sensing (CS) techniques, the imaged scene was reconstructed by fewer coded measurements compared to the image size. We demonstrated that the proposed single-pixel imaging system framework could significantly improve the imaging efficiency and resolution.

Tu-Po2-85
The Design Of W Band Dual Polarization Parabolic High Gain Antenna
Zhengxin Fang; Sen Feng
ECEIEE, China

In this paper, a dual-polarization parabolic high-gain antenna in the W-band is designed. Dual polarized horn is used as feeds in the antenna in the antenna systems. A microstrip reflection array is attached to the parabolic column as a reflective surface. The antenna has dual polarization. In the azimuth direction, phase compensation is performed by the microstrip reflection array applied to the inner surface of the parabolic column, and lobe focusing is achieved together with the dual-polarized horn feed, in the elevation direction, lobe focusing is achieved by means of a parabolic surface on the elevation surface and a dual-polarized horn feed, the W-band far-field pattern is thus obtained. The antenna is 0.6m long and 0.6m wide. After tested, the sidelobe level is â?¤-25dB, the cross polarization is <-30dB, and the gain is >52.5dB in the bandwidth of 93.5GHz-95.5GHz. The antenna has compact structure, small volume, light weight, it is simple feeding, low cost .

Tu-Po2-86
Comparative Study Of Millimeter Wave III/V Semiconductor And Integrated Silicon Based FMCW Radars
Jean-Paul Guillet¹; Frédéric Fauquet²; Jing Shun Goh²; Adrien Chopard²; Jean-Baptiste Perraud²; Marie Roux³; Patrick Mounaix^2
1Laboratoire IMS / Université de Bordeaux / CNRS UMR 5218, France; ²IMS Laboraotry, France; ³Atelier des renaissances, France

In this publication, we present comparative study of the last developments of frequency modulated continuous wave (FMCW) systems in the terahertz frequency range including GaAs based systems and SiGe integrated systems.

Tu-Po2-87
Study Of A THz Hollow-core Fiber For Sample Reflectance Analysis
Mingming Pan¹; Cristiano M. B. Cordeiro²; Frédéric Fauquet¹; Patrick Mounaix¹; Gildo S Rodrigues²; Marcos A. R. Franco³; Jean-Paul Guillet^4
1IMS Laboraotry, France; ²Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, Brazil; ³Instituto Tecnológico de Aeronáutica-ITA, Brazil; ⁴Laboratoire IMS / Université de Bordeaux / CNRS UMR 5218, France

We investigated a 3D printed hollow-core THz waveguide with a suitable frequency band to be, in the future, associated with a guided reflectometry system.

Tu-Po2-88
Cooled Silicon-On-Insulator Diode Thermometer: Toward THz Passive Imaging
Jérémy Blond; Jérôme Meilhan; Abdelkader Aliane; Laurent Dussopt
CEA LETI, France

Terahertz passive imaging requires high sensitivity detectors, with Minimum Detectable Power (MDP) under the picowatt range. An antenna-coupled cooled microbolometer, incorporating a lateral PiN-like diode as thermometer, could represent a solution. In a first step, such diode performances have to be investigated, especially the temperature coefficient of current (TCC) and the low frequency noise. Prototypes were fabricated on Silicon-On-Insulator (SOI) 4" wafers with 50-nm active silicon layer. I-V and noise measurements down to 81K were useful to derive the electrical MDP of the future bolometer, already reaching 6.6 pW at 10 frames per second.

Tu-Po2-89
Continuous-wave Terahertz Computed Tomography Based On Bessel Beam
Lu Rong; Bin Li; Dayong Wang; Yunxin Wang; Jie Zhao; Xiaoyu Shi
Beijing University of Technology, China

We report a continuous-wave terahertz computed tomography using Bessel beam generated by the axicon. Two-dimensional cross-sectional images of the internal structure of plastic pipes at different distances are reconstructed by using the filtered back projection algorithm. Compared with conventional Gaussian beam, Bessel beam can extend the depth of field and improve the fidelity of the reconstruction.

Tu-Po2-90
Diffraction Of Terahertz Gaussian And Bessel Beams On 2D Gratings With Wavelength-Scale Openings
Oleg Kameshkov; Boris Knyazev; Igor Kotelnikov; Boris Goldenderg
Budker Institute of Nuclear Physics, Russian Federation

The diffraction of Gaussian and arbitrary-order Bessel wavefronts on the 2D periodic amplitude and phase gratings, including those with holes whose diameters are close to the wavelength, was investigated. When the amplitude grating is illuminated by a Bessel beam, the self-images of the grating in the main and fractional Talbot planes turn into lattices of rings whose radii depend in a complex way on the grating parameters and on the illuminating beam characteristics. The results of the experiments carried out using the wavelength-tunable radiation of the Novosibirsk free electron laser (NovoFEL) are in good agreement with the numerical calculations and the analytical model developed.

Tu-Po2-91
High Resolution Passive THz Imaging Array With Polarization Reusage In 22nm CMOS
Sven van Berkel; Satoshi Malotaux; Bart van den Bogert; Marco Spirito; Daniele Cavallo; Andrea Neto; Nuria Llombart
Delft University of Technology, Netherlands

A 12-pixel THz Focal Plane Array (FPA), integrated in Global Foundries 22nm CMOS technology, enabling high resolution passive THz imaging, is presented. The array efficiently couples blackbody radiation from 200 GHz to 600 GHz to Schottky Barrier Diodes (SBDs) in a differential topology. An antenna-detector co-design results in an average Noise Equivalent Power (NEP) of 0.9 pW/√Hz. An extremely small array periodicity is achieved by using two orthogonal polarizations. Such configuration enables passive imaging with a near-diffraction limited resolution while simultaneously maintaining a high optical efficiency of 42%. The array is currently in tape-out and measurements will be presented at the conference.

Tu-Po2-92
Full-field THz Polarimetric Imaging With THz Quantum Cascade Laser And THz Imager
Takahiko Mizuno¹; Takuya Moriki²; Masatomo Yamagiwa²; Takeo Minamikawa¹; Takeshi Yasui^1
1Institute of Post-LED Photonics, Tokushima University, Japan; ²Faculty of Mechanical Engineering, Tokushima University, Japan

We demonstrate full-field THz polarimetric imaging with THz quantum cascade laser and THz imager. In contrast to point-scanning THz polarization imaging based on THz-TDS, the demonstrated method does not need mechanical stages for time-delay scanning and sample-position scanning. Due to no mechanical scanning, the fill-field polarimetric images are acquired with moderate frame rate.

Tu-Po2-93
Quantum Probability Theory Applied To Improve Terahertz Imaging Quality
Xuling Lin¹; Zhi Zhang¹; Jianbing Zhang²; Zhimin Dai^2
1Beijing Institute of Space Mechanics and Electricity, China; ²Shanghai Institute of Applied Physics, Chinese Academy of Sciences, China

THz imaging plays an important role in astronomy, atmospheric remote sensing and biological identification. Improvement of imaging quality is of great significance to the application of terahertz imaging system. In this paper, on the basis of quantum probability statistics, an image enhancement method for improving terahertz imaging quality is proposed. Experimental results show that this method takes account of both global and local image information, and improves the quality of terahertz image effectively.

Tu-Po2-94
Terahertz Digital Holography Using Field-Effect Transistor Detectors
Yuchen Zhao¹; Dmytro But²; Marc Georges¹; Wojciech Knap^3
1Centre Spatial de Liège, Université de Liège, Belgium; ²Center for Terahertz Research and Applications (CENTERA), Institute for High Pressure Physics,Polish, Poland; ³Laboratory Charles Coulomb, Montpellier University, France

We report on the experimental realization of digital holography at 140 GHz using terahertz detectors based on field-effect transistors. We demonstrate that hologram signal can be efficiently recorded by the FET detector at room temperature. The digital reconstructions of amplitude and phase objects are presented. Owing to the possibility for FET array integration and massive production, potential towards fast scan nondestructive testing application is discussed.

Tu-Po2-95
Genetic Algorithm Based Optimization For Terahertz Time-Domain Adaptive Sampling
Kaidi Li¹; Xuequan Chen¹; Rui Zhang²; Emma Pickwell-MacPherson³; Shuaiqi Shen¹; Kai Liu^1
1The Chinese University of Hong Kong, China; ²Shenzhen Institutes of Advanced Technology, Chines Academy of Science, China; ³The Chinese University of Hong Kong, Hong Kong and Department of Physics, The University of Warwick, the United Kingdom

We propose an approach based on a genetic algorithm (GA) to improve the sampling efficiency in terahertz time-domain spectroscopy (THz-TDS). The experimental results show that our approach can greatly reduce the sampling time whilst maintain a very high accuracy compared to high-resolution step scanning. Moreover, this approach can be easily implemented in most TDS systems equipped with a delay stage without any hardware cost. The accuracy, flexibility and efficiency indicate great potential for this approach to improve the scanning speed in a wide range of applications.

Tu-Po2-96
Hybrid Technique For Gas Sensing Based On Differential Cavity Ring Down Spectroscopy Sensitized With Thermal Lens Effect
Atsushi Yarai
Osaka Sangyo University, Japan

A new gas sensing technique based on a cavity ring down (CRD) spectroscopy is proposed. This technique features the hybrid operation for enhancing the sensitivity by amplifying the optical absorption efficiency with a thermal lens effect. At first, system configuration composed of optical fiber is presented. Then, the observed comb-like differential CRD signal which exhibits its capability definitely is shown. It is confirmed that the detectability is approximately 20 μmol/liter as the limit of detection value with P(13) absorption line of acetylene gas. It is a few-fold higher value compared with our conventional technique.

Tu-Po2-97
Metasurface-Based Anti-Alias Filters For Improved THz-TDS Measurements
Nazar Nikolaev¹; Sergei Kuznetsov²; Alina Rybak³; Shang-Hua Yang^4
1Institute of Automation and Electrometry SB RAS, Russian Federation; ²Rzhanov Institute of Semiconductor Physics SB RAS, Russian Federation; ³Novosibirsk State University, Russian Federation; ⁴Department of Electrical Engineering, National Tsing Hua University, Taiwan

We propose an approach to improve THz-TDS low-frequency measurements accuracy. It is based on applying anti-alias filters to narrow the frequency band of the THz signal that allows increasing the sampling interval in accordance with the Nyquist--Shannon theorem. The concept was verified by studying the transmittance spectra of the reference samples -- band-pass THz filters centered at 156 and 376 GHz. We show a reduction of the spectrometer scanning time by up to 12 times while maintaining the measurement accuracy. The prospects for using this approach to increase the dynamic range and the signal-to-noise ratio of the spectrometer in the subterahertz range are discussed.

Tu-Po2-98
Optical Heterodyne Detection In The Terahertz Region For Accurate Frequency Measurement
Shin'ichiro Hayashi; Shingo Saito; Norihiko Sekine
National Institute of Information and Communications Technology, Japan

We propose an optical heterodyne detection in the terahertz region using parametric up-conversion in a nonlinear LiNbO3 crystal for accurate frequency measurement. Nonlinear wavelength up-conversion techniques based on frequency stabilized infrared pumping beam allow the spectra in the terahertz region to be determine their frequency and intensity. These are very promising for extending applied research into the terahertz region, and we expect that these will open up new research fields such as wireless information communications in the terahertz region.

Tu-Po2-99
Combination Of Adaptive Sampling Terahertz Dual-Comb Spectroscopy With A Free-Running Single-Cavity Dual-Comb Fiber Laser
Jie Chen; Kuzuki Nitta; Xin Zhao; Takahiko Mizuno; Takeo Minamikawa; Zheng Zheng; Takeshi Yasui
Beihang University, China

Mode-resolved adaptive sampling terahertz dual comb spectroscopy is demonstrated using a free-running wavelength-multiplexed dual-comb fiber laser, indicating the capability of such single-cavity dual-comb sources for high-precision THz spectroscopy.

Tu-Po2-100
Frequency Measurement For Terahertz Waves Based On The High Magnetic Field Technology
Xin Qi; Houxiu Xiao; Xiaotao Han; Donghui Xia; Pengbo Wang; Xianfei Chen
Huazhong University of Science and Technology, China

A novel method based on the Zeeman Effect has been proposed for the frequency measurement in the THz range. We convert the frequency measurement into magnetic field measurement. In theory, the measurement range can cover the entire THz range as the magnetic field meets the requirement. Using this method, we demonstrate an accuracy of our measurement system as high as 0.01% for the measurement of a 120GHz source, no matter it work at a continuous regime or a pulse regime.

Tu-Po2-101
Uncertainty Quantization Of Fano Resonance Frequency Shift Measurement
Tuan Anh Pham Tran; Elana Pereira de Santana; Peter Haring Bolívar
University of Siegen - High Frequency and Quantum Electronics, Germany

We describe and characterize a Fano-resonance frequency shift measurement setup at 300GHz for ex-situ biomolecule detection applications. By quantifying experimental contributions from each uncertainty source, trade-offs can be adapted to achieve the desired system stability requirements. We obtain a 10 MHz standard deviation in determining resonance position with repeated sample exchange and repositioning, and determine the future to attain a 2 MHz frequency shift precision at 300GHz.

Tu-Po2-102
Dual-band Electromagnetically Induced Transparency Effect In Asymmetrically Coupled Terahertz Metamaterials
Dipa Ghindani¹; Rakesh Sarkar²; Monika Devi Koijam²; Ravikumar Jain³; Arnab Pattanayak³; Shriganesh Prabhu³; Gagan Kumar^2
1Tata Institute of Fundamental Research, India; ²Department of Physics, Indian Institute of Technology Guwahati, India; ³Tata Institute of Fundamental Research, Foton Lab, India

In this article, we propose a metamaterial geometry capable of exhibiting dual-band electromagnetic induced transparency (EIT) effect in terahertz frequency regime. The meta-molecule unit consists of two C resonators of different dimensions, placed alternately on both sides of a cut-wire (CW). Our study can play an important role in the development of multi-band slow light devices and also for sensing applications.

Tu-Po2-103
THz Wave Generation In Nonlinear Crystal ?eta-BBO
Jingguo Huang¹; Zhiming Huang¹; Yury Andreev²; Grigory Lanskii²; Dmitrii Lubenko³; Nazar Nikolaev⁴; Valery Losev^3
1Shanghai Institute of Technical Physics CAS, China; ²Institute of Monitoring Climatic and Ecological Systems SB RAS, Russian Federation; ³Institute of High Current Electronics SB RAS, Russian Federation; ⁴Institute of Automation and Electrometry SB RAS, Russian Federation

Nonlinear crystals of beta-barium borate, beta-BBO (further BBO) are widely used to generate THz radiation in a laser filament in two-color optical systems, in which BBO is used to for the second harmonic generation of the pump radiation. It should be outlined that BBO crystal can be used for frequency conversion of visible - IR laser emissions into the THz range in accordance with the recent study. Possessing high damage threshold, despite of low nonlinear coefficients, BBO crystal can be considered as an effective nonlinear crystal for THz generation by parametric nonlinear processes. In this experiment, the THz pulses are realized from BBO crystal pumped by 10-mJ Ti: Sapphire laser complex operating at 950 nm at room temperature. Generation is achieved in spectral range 0.25-0.8 THz.

Tu-Po2-104
15NH3 Terahertz Gas Laser Pumped By A Mid-infrared Quantum-Cascade Laser
Martin Wienold; Alsu Zubairova; Heinz-Wilhelm Hübers
German Aerospace Center (DLR), Germany

We present an optically pumped terahertz gas laser, which is based on a distributed-feedback mid-infrared quantum-cascade laser as a pump source, a standing wave resonator, and 15NH3 as a gain medium.

Tu-Po2-105
High Performance Terahertz Absorption Of Nanostructured NiCr Film For A Pyroelectric Detector
Ziji Liu; Zhiqing Liang; Xing Zheng; Yadong Jiang
University of Electronic Science and Technology of China, China

Nanostructured metallic films is an effective THz absorption layer for pyroelectric detectors.The THz responsivity for detector tested by lock in amplifier reaches 8.38Ã-104V/W and the lowest noise equivalent power value(NEP) reaches 1.27Ã-10-10W/Hz1/2 at 20Hz operating frequency use 2.52THz radiation, which is suitable for THz imaging application. Meanwhile it provides a feasible approach for fabricating high responsivity THz detector

Tu-Po2-106
A Novel Terahertz Microfluidic Chip
Bo Su; Jiahui Wang; Yiwei Wen; Jingsuo He; Shengbo Zhang; Cunlin Zhang
Capital Normal University, People's Republic of China, China

we fabricate a new terahertz microfluidic chip, which can detect liquid samples using THz-TDS system or asynchronous optical sampling system. The chip has a sandwich structure, and consists of substrate, cover and microchannel layer. The substrate and cover are made of two materials, PMMA and cycloolefin copolymers (COC). The microchannel layer is fabricated by PDMS. Through van der Waals force, the substrate, cover and microchannel layer are sealed together. We use the chip to study the transmission of terahertz to deionized water and the influence of different kinds and concentration of electrolyte solution on hydrogen bond in aqueous solution, and the results prove the feasibility of this method.

Tu-Po2-107
Quasi-Optical Design Of ECRH Mirrors For ITER First Plasma Operations
Francesco Fanale¹; Alessandro Bruschi¹; Olivier Darcourt²; Daniela Farina¹; Lorenzo Figini¹; Franco Gandini³; Mark Andrew Henderson³; Ryan Hunt³; Alessandro Moro¹; Paola Platania¹; Burkhard Plaum^4
1Consiglio Nazionale delle Ricerche - Istituto di Fisica del Plasma, Italy; ²Arial Industries, France; ³ITER Organization, France; ⁴Universität Stuttgart - Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Germany

A set of components will be installed during ITER fist plasma operation to protect the vacuum vessel and other in-vessel auxiliary systems from the plasma and from the stray radiation injected at the Electron Cyclotron harmonics to generate breakdown and sustain burn-through. This paper focuses on the quasi-optical design of the system of three mirrors redirecting the microwave beams coming from the Electron Cyclotron Resonance Heating (ECRH) upper launcher to the plasma resonance after proper shaping. In particular, the system consists of two shaped mirrors and one grating mirror. The non-absorbed EC power is then intercepted and absorbed into a beam dump located in one equatorial port.

Tu-Po2-108
Terahertz Filter With Flat-top Transmission Response
Antonio Ferraro¹; Alfonso A. Tanga²; Dimitrios C. Zografopoulos¹; Gabriele C. Messina³; Michele Ortolani²; Romeo Beccherelli^1
1Consiglio Nazionale delle Ricerche - Istituto per la Microelettornica e Microsistemi CNR-IMM, Italy; ²Department of Physics, Sapienza University of Rome, Italy; ³Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi (CNR-ISC), Italy

A new terahertz filter based on the coupling of guided-mode resonances and Fabry-Perot resonance is presented resulting in a flat top response. The spectral response lies in the sub-THz communication windows with central frequency of 300 GHz. The filter performance shows high transmittance, with less than 3dB losses, and high out-of-band rejection. The filter is fabricated via standard photolithography on thin films of the Zeonor polymer. This typology of THz components provides a cost-effective functional solution for narrowband filtering in emerging THz devices and systems for telecommunication.

Tu-Po2-109
Polarization And Sectioning Characteristic Of THz Confocal Microscopy
Min Wan¹; Dovilė Čibiraitė²; Bing Li³; Hui Yuan²; Viktor Krozer²; Hartmut Roskos²; Da Yong Wang³; John Sheridan^1
1School of Electrical & Electronic Engineering, University College Dublin, Ireland; ²Physikalisches Institut, Goethe University Frankfurt, Germany; ³College of Applied Sciences, Beijing University of Technology, China

A 300 GHz confocal microscope has been implemented and tested consistent lateral and axial spatial resolution under difference polarization have been demonstrated.

Tu-Po2-110
Generation And Measurement Of Traceable THz Frequencies
Gregory Gäumann; Jacques Morel
Federal Institute of Metrology METAS, Switzerland

The THz radiation is generated by optical heterodyning of two lasers in a phomixer and the frequency traceability is achieved either by measuring the laser frequencies with a traceable wavemeter or by directly referencing the two lasers to a self-referenced optical frequency comb (OFC) locked to an atomic clock. This method will allow achieving a relative THz frequency uncertainty below 8?10-9.

Tu-Po2-111
Tail-suppressed THz Photocurrent By A Bi-polar Photoconductive Antenna Fabricated On Semi-insulating GaAs
Anup Kumar Sahoo¹; Hsiao-Hua Wu²; Yu-Cheng Hong¹; Yu-Chen Chang¹; Osamu Wada³; Ci-Ling Pan^1
1Department of Physics, National Tsing Hua University, Taiwan; ²Department of applied physics, Tunghai University, Taiwan; ³Office for Academic and Industrial Innovation (Oacis), Kobe University, Japan

We designed and fabricated bi-polar type photoconductive antenna (PCA) for efficient generation of broadband terahertz (THz) radiation. The falling time of overlayingly generated photocurrent from bi-polar PCA can be achieved 200 fs via superimposing two primariy opposite polarity photocurrent pulses having falling time of 100 ps with time delay of 200 fs. The simulation results disclosed a possibility to shift the central frequency from 0.1 to 1.3 THz and enhance the THz power by twice in the range 1.5 - 3.3 THz by using low cost substrate with long carrier life time such as semi-insulating gallium arsenide (SI-GaAs).

Tu-Po2-112

THz To Inspect Graphene And Thin Film Materials
Álvaro Cordón¹; Luis Miranda¹; Cristian Martínez¹; Andrea Inés¹; David Etayo¹; Montserrat Fernández¹; Pablo Rodríguez¹; Elena Taboada¹; Albert Redó-Sánchez¹; Mónica Castrillo¹; Miguel A. G. Laso²; Israel Arnedo^1,2
1Das-Nano, Spain; ²Universidad Publica de Navarra (UPNA), Dept. Electrical, Electronic and Communications Eng., Spain

In this paper, we present a system that provides meso-scale characterization of thin film materials, covering the gap between nano-scale and macro-scale methods. Nano-scale methods are slow and cannot characterize large surfaces. Macroscale methods generate characterization that averages the magnitudes and, thus, cannot provide localized information. Our system works in reflection as opposed to state-of-the-art methods and provides mobility, carrier density, and conductance maps in the THz range. Moreover, it can be integrated with reactors and enables monitoring of the fabrication of materials in real-time, supporting, for instance, the production of graphene at industrial scale.

Tu-Po2-113
Excitonic Terahertz Emission From Silicon At Steady-State Interband Photoexcitation
Alexey Zakhar'in; Alexander Andrianov
Ioffe Institute, Russian Federation

Terahertz range photoluminescence from specially designed structures with tunnel coupled double quantum wells under interband optical excitation has been investigated. A series of narrow emission lines were observed and interpreted as intersubband radiative transitions between electron quantum confinement levels.