Wednesday 4 September 2019

 

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

Chairperson: Jean Léotin

09:00 We-Pl-1

Terahertz Physics Of Graphene, Possibly The Most Nonlinear Material We Know

Dmitry TURCHINOVICH, Bielefeld University, Germany

09:45 We-Pl-2 Optically-Pumped Terahertz Sources And Applications

Jean-François LAMPIN, IEMN Lille, France

10:30-11:00 - Coffee Break

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

11:00-12:30 -  We-AM-1- THz Water - Room 101

Chairperson: Xavier Ropagnol

11:00 We-AM-1-1
Hertz-to-terahertz Dielectric Response Of Nanoconfined Water Molecules
Mikhail Belyanchikov¹; Maxim Savinov²; Petr Bednyakov²; Zakhar Bedran¹; Victor Thomas³; Victor Torgashev⁴; Anatoly Prokhorov¹; Alois Loidl⁵; Peter Lunkenheimer⁵; Elena Zhukova¹; Ece Uykur⁶; Martin Dressel⁶; Boris Gorshunov^1
1Moscow Institute of Physics and Technology, Russian Federation; ²Institute of Physics AS CR, Czech Republic; ³Institute of Geology and Mineralogy RAS, Russian Federation; ⁴Southern Federal University, Russian Federation; ⁵University of Augsburg, Germany; ⁶Universität Stuttgart, Germany

Broad-band dielectric spectroscopy is applied to study excitations of interacting electric dipoles spatially arranged in a network with an inter-dipole distance of 5-10 Å. The dipoles with magnitude of 1.85 Debye are represented by single H2O molecules located in voids (0.5 nm size) formed by ions of the crystal lattice of beryl and cordierite. Rich sets of single-particle and collective excitations are discovered and their origin analyzed.

11:30 We-AM-1-2
Collective Dynamics Of Nanoconfined Water In Phospholipid Multilamellar Vesicles Studied By Broadband Dielectric Relaxation Spectroscopy
Kihoon Eom; Jeongmin Jang; Seonmyeong Kim; Gun-Sik Park
Seoul National University, Republic of Korea

We present the first experimental characterization, using GHz to THz dielectric relaxation spectroscopy, of the collective rearrangement of the hydrogen bond network of water molecules nanoscopically confined in phospholipid multilamellar vesicles. We determined a distinct relaxation peak at ~40 GHz and the Kirkwood correlation factor of approximately 1.13, which are the indication of acceleration of the collective reorientation dynamics with nanoconfinement, and complete disruption of the hydrogen bond network compared with that of bulk water. Combined with X-ray observation, it has estimated that ~68% of the nanoconfined water contributes to the accelerated relaxation mode.

11:45 We-AM-1-3
Intermolecular Probe For The Structural Deformation Of Liquid Water Around Highly Charged Ions
Vasileios Balos; Martin Wolf; Mohsen Sajadi
Fritz Haber Institute of the Max Planck Society, Germany

We employ nonlinear THz spectroscopy to study the impact of highly charged ions on the hydrogen-bonding network of liquid water. We monitor the change of the THz induced optical birefringence of water in the presence of strongly charged anions and cations. We correlate the ionic effect to the strengthening / weakening of the coupling between the rotational and the translation motions in the liquid. The latter intermolecular probe, clearly shows opposite anionic versus cationic effect and enable us to provide a novel insight on the structure making / breaking behavior of ions.

12:00 We-AM-1-4
Quantum Critical Behavior Of Nanoconfined Water Molecules
Elena Zhukova¹; Mickhail Belyanchikov¹; Maxim Savinov²; Peter Bednyakov²; Jan Prokleska²; Stanislav Kamba²; Zakhar Bedran¹; Victor Thomas³; Victor Torgashev⁴; Ece Uykur⁵; Martin Dressel⁵; Boris Gorshunov^1
1Moscow Institute of Physics and Technology, Russian Federation; ²Institute of Physics AS CR, Czech Republic; ³Institute of Geology and Mineralogy, RAS, Russian Federation; ⁴Faculty of Physics, Southern Federal University, Russian Federation; ⁵Physikalisches Institut, Universität Stuttgart, Germany

We have studied terahertz and radio-frequency dielectric response of single water molecules periodically arranged in nano-cages formed by the crystal lattice of beryl. Below ~20 K, quantum effects start to dominate the properties of the H2O dipolar system as manifested by a crossover between the Curie-Weiss and the Barrett regimes in the temperature behavior of the dielectric permittivity ε'. Analyzing the temperature evolution of the inverse permittivity ( ε')^-1 down to T = 0.3 K, we discover signatures of quantum critical behavior of coupled water molecular dipoles: its quadratic variation with temperature at T=3-12 K and a shallow minimum in the ( ε')^-1(T) dependence below 3 K.

12:15 We-AM-1-5
Hydration Numbers From Ab Initio Water Reorientation Dynamics
Seonmyeong Kim¹; Jeongmin Jang¹; Kihoon Eom¹; Devis Di Tommaso²; Gun-Sik Park^1
1Seoul National University, Republic of Korea; ²Queen Mary University of London, United Kingdom

We present a novel approach to determine the hydration number of aqueous electrolytes by means of ab initio molecular dynamics. An hydration status analysis is devised to quantify the cooperative effect of ions on the reorientational dynamics of different water subpopulations in electrolyte solutions. The methodology is applied to predict the hydration numbers, h, as the number moles of water molecules per mole of dissolved salt that no longer participate in bulk-like reorientational dynamics. The obtained hydration number of MgCl2 (h = 15) is consistent with THz-DR experiment, measuring reorientational dynamics of water in solutions. By providing a link with the micro-scale dynamical behaviour of ions and water molecules, this approach represents a generally applicable, well-defined methodology to quantify hydration numbers of ions and molecules in aqueous solutions.

11:00 - 12:30 We-AM-2 - PC Devices 1 - Room 162

Chairperson: Nuria Llombart-Juan

11:00 We-AM-2-1
Highly Efficient Scalable Semiconductor Terahertz Sources
Gyula Polonyi¹; Priyo Nugraha¹; Nelson Mbithi¹; Gergő Krizsán¹; Balázs Monoszlai²; György Tóth¹; Mátyás Mechler¹; János Hebling¹; József Fülöp^1
1University of Pécs, Hungary; ²ELI-ALPS, ELI-Hu Nonprofit Ltd., Hungary

Highly efficient generation of intense THz pulses from infrared-pumped semiconductor sources is presented. Concepts of increasing the efficiency and peak electric fields for single- and multicycle THz waveforms are discussed.

11:30 We-AM-2-2
Generation Of A Guided Mode In A THz Semiconductor Waveguide using Excitation By A Tilted Optical Pulse Front
Gamar-ul Islam; Fanqi Meng; Hartmut G Roskos
Goethe University Frankfurt, Physikalisches Institut, Germany

We employ tilted-pulse-front techniques to control the propagation direction of the THz pulses emitted from photoexcited semiconductors. At a proper tilt angle of the optical pulse front, the generated THz pulse propagates along a waveguide on the semiconductor surface and eventually emits from the end facet of the semiconductor structure. This work aims at an investigation of semiconductor quantum structures with gain excited just in time when the THz pulse to be amplified arrives

11:45 We-AM-2-3
Advanced Photoconductive Terahertz Near-field Microprobes For 1550 Nm Wavelength Operation Based On InGaAs:Rh
Michael Nagel¹; Alexander Michalski¹; Simon Sawallich¹; Robert B. Kohlhaas²; Björn Globisch^2
1Protemics GmbH, Germany; ²Heinrich Hertz Institut, Germany

Photoconductive microprobes have been widely established in recent years for surface-near THz field measurements with sub-wavelength resolution and applications such as wafer scanning or metamaterial characterization. Since the standard material for these probes is still LT-GaAs, the optical pump wavelength is usually set below 890 nm for direct bandgap excitation. Adaption to modern fiber-based THz TDS systems --operating at 1550 nm -- required the use of optical frequency doubling components, so far. In this work, we investigate an alternative solution based on InGaAs:Rh for direct operation at 1550 nm wavelength.

12:00 We-AM-2-4
Photoconductive Arrays For High-Field Terahertz Generation
David Bacon; Mark Rosamond; Thomas Gill; Andrew Burnett; Lianhe Li; John Cunningham; Edmund Linfield; Giles Davies; Paul Dean; Joshua Freeman
University of Leeds, United Kingdom

We report on the development of a large-area photoconductive THz array structure with an LT-GaAs active region fabricated on quartz substrates using a BCB bonding process. These generate high THz-fields with a bandwidth greater than 5 THz.

12:15 We-AM-2-5
Rapid, Accurate And Precise Terahertz Polarization Modulation And Ellipsometry With Multi-pixel Interdigitated Photoconductive Emitters
Connor Mosley; Michael Staniforth; Arturo Hernandez-Serrano; Emma Pickwell-MacPherson; James Lloyd-Hughes
University of Warwick, United Kingdom

We demonstrate that multi-element interdigitated photoconductive emitters can rapidly and precisely modulate broadband terahertz radiation between linear (horizontal or vertical) and circular polarization states. The rapid electrical modulation between polarization states is beneficial for THz time-domain spectroscopic ellipsometry: it eliminates mechanical rotation and enhances the relevant figures of merit.

11:00 - 12:30 We-AM-3 - High Fields 3 - Amphi Lavoisier

Chairperson: Koichiro Tanaka

11:00 We-AM-3-1

Examining Nonlinear Terahertz Photonic And Phononic Excitation With Two-Dimensional Spectroscopy
Brittany E. Knighton; Megan Nielson; Courtney L. Johnson; Lauren Rawlings; Aldair Alejandro; R. Tanner Hardy; Clayton D. Moss; Jeremy A. Johnson
Brigham Young University, United States

We use high-field, broadband terahertz (THz) pulses to nonlinearly excite a set of Raman active modes in centrosymmetric crystals. Using two-dimensional (2D) THz spectroscopy we can investigate photonic and phononic excitation and isolate the dominant and secondary nonlinear excitation pathways. We present a general framework for 2D THz vibrational spectroscopy in solid systems that provides important clarification for the growing new field of nonlinear phononics.

11:30 We-AM-3-2
Cavity Enhanced Third Harmonic Generation From Si:B Pumped With Intense Terahertz Pulses
Fanqi Meng¹; Mark D. Thomson¹; Bernhard Klug¹; Qamar ul-Islam¹; Alexej Pashkin²; Harald Schneider²; Hartmut G. Roskos^1
1J. W. Goethe-Uni Frankfurt, Germany; ²Helmholtz-Zentrum Dresden-Rossendorf, Germany

we report the third harmonic generation (THG) of the terahertz free electron laser (FEL) pulses from Si:B at cryogenic temperature. The measured χ3 increases as a function of the pumping terahertz intensity. The physical mechanism of the THG is attributed to the free-carrier χ3 nonlinearity due to non-parabolicity of the valance band, where χ3 increases as a function of the carrier density. The free carriers are generated via impact ionization of the frozen boron dopants under irradiation of the FEL pulses. By positioning the Si:B in a one-dimensional photonic crystal (1D PC) cavity, the measured THG intensity increases by about 200 times.

11:45 We-AM-3-3
Terahertz-Induced Electron Emission From A Gold Surface
Shaoxian Li¹; Priyo Nugraha¹; Ashutosh Sharma²; Csaba Lombosi³; Zoltan Ollmann¹; Istvan Marton⁴; Gyozo Farkas⁴; Janos Hebling¹; Peter Dombi⁴; Fulop Jozsef^5
1Szentágothai Research Centre, University of Pécs, Hungary; ²ELI-ALPS, Hungary; ³University of Pécs, Hungary; ⁴MTA "Lendület" Ultrafast Nanooptics Group, Wigner Research Centre for Physics, Hungary; ⁵MTA-PTE High-Field Terahertz Research Group, Hungary

Electron emission was observed at moderate THz peak field strengths below 50 kV/cm. Flipping the polarity of the THz pulses resulted in a significantly different current signal. The electron signal, also measured as function of the THz polarization angle, showed double maxima. In order to compare the photoemission measurement results with the theoretical model, we employed the Fowler-Nordheim (FN) equation along with the classical equation of motion. The enhanced photocurrent with polarity flip (while using the symmetric waveform of THz field) indicates towards rescattering process. In order to investigate the effect of rescattering we numerically solved the time dependent Schrodinger equation to find the emission current probability quantum mechanically.

12:00 We-AM-3-4
Ultrafast Magnetic Recording With Terahertz Light
Ilie Radu¹; Mostafa Shalaby²; Martin Hennecke¹; Wolfgang Engel¹; Clemens KorffSchmising¹; Tsukamoto Arata³; Christoph Hauri⁴; Stefan Eisebitt^1
1Max Born institute, Germany; ²Swiss Terahertz LLC, Switzerland; ³College of Science and Technology, Nihon University, Japan; ⁴Paul Scherrer Institute, Switzerland

We report on the first demonstration of ultrafast magnetisation switching of a spin-ordered material using single-cycle, intense THz pulses at a central frequency of 2 THz.

12:15 We-AM-3-5
Nonlinear THz Field Applications In Free Space
Anastasios Koulouklidis¹; Claudia Gollner²; Valentina Shumakova²; Vladimir Fedorov³; Audrius Pugzlys²; Andrius Baltuska²; Stelios Tzortzakis^4
1Institute of Electronic Structure and Laser (IESL)/ Foundation for Research and Technology-Hellas (F, Vassilika Vouton, Greece; ²Photonics Institute/TU Wien, Austria; ³Science Program/Texas A&M University at Qatar, Qatar; ⁴Department of Materials Science and Technology/University of Crete, Greece

Here we demonstrate that intense free space THz fields can nonlinearly induce excitonic photoluminescence in two semiconductors as well as strong cross-phase modulation in an electro-optic crystal.

11:00-12:30 - We-AM-4 - QCL 3 - Room 151

Chairperson: Sukhdeep Dhillon

11:00 We-AM-4-1

Independent Control Of Mode Selection And Power Extraction In Terahertz Quantum Cascade Lasers
Chenren Yu¹; Huan Zhu¹; Haiqing Zhu¹; Gaolei Chang¹; Fangfang Wang¹; Jianxin Chen¹; Lianhe Li²; A. Giles Davies²; Edmund H. Linfield²; Gangyi Xu¹; Li He^1
1Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, China; ²School of Electronic and Electrical Engineering, University of Leeds, United Kingdom

We demonstrate novel THz quantum cascade lasers with a gain endowed photonic crystal (PhC) and a grating coupler (GC) formed on each end of the ridge. The PhC acts as a reflection mirror with extremely narrow bandwidth, and the GC enables high radiation efficiency. Such configuration independently controls the mode control and power extraction, and results in stable single mode emission with very high output power. The peak output power reaches to 366 mW at 20K, and remains 224 mW at 77K, measured in pulsed mode.

11:30 We-AM-4-2
THz Quantum Cascade Lasers With Optimized Beam Divergence
Junqi Liu; Jinchuan Zhang; Fengqi Liu; Fangyuan Zhao
Institute of Semiconductors, Chinese Academy of Sciences, China

Single-mode surface-emitting terahertz quantum cascade lasers based on distributed feedback mechanism with high symmetry is presented. By inserting a central Ãfââ?s¬-phase shift or using a non-uniform grating period, an optimized 2-D far-field radiation pattern is obtained. Single-mode emission is achieved with a side-mode suppression ration above 25 dB.

11:45 We-AM-4-3
Dispersion And Ridge Width Effect In Terahertz Quantum Cascade Laser Combs
Wenjian Wan; Kang Zhou; Ziping Li; Xiaoyu Liao; Juncheng Cao; Hua Li
Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, China

The ridge width effect on comb operation of single plasmon waveguide quantum cascade lasers emitting around 4.2 THz is studied by simulation and experiments. The total group velocity dispersion (GVD) is numerically evaluated for 6-mm-long lasers with ridge widths. The simulation reveals that the clamped gain dispersion strongly contributes to the total GVD and the laser with a 150-ÃfŽÃ,¼m-wide ridge shows the flattest total GVD in the lasing range. The optimal ridge width of 150 ÃfŽÃ,¼m for comb operation is also experimentally verified.

12:00 We-AM-4-4
Patch Antenna Microcavities THz Quantum Cascade Lasers
Joel Perez-Urquizo¹; Julien Madeo¹; Yanko Todorov²; Lianhe Li³; Alexander G. Davies³; Edmund Linfield³; Carlo Sirtori²; Keshav Dani^1
1Okinawa Institute of Science and Technology, Japan; ²Ecole Normale Supérieure ENS, Université de Paris, France; ³University of Leeds, United Kingdom

We study the emission of THz quantum cascade lasers (QCLs) designed in arrays of Patch Antenna Microcavities (PAM). The array geometry is an effective strategy to control the losses and to achieve phase locking, allowing for beam shaping and high photon outcoupling efficiency. We demonstrate a 40-fold enhanced emission compared to standard ridge waveguides and a gaussian beam divergence as low as 2° x 2°.

12:15 We-AM-4-5
High-Speed Modulation Of A Terahertz Quantum Cascade Laser Using Coherent Acoustic Phonon Pulses
Aniela Dunn¹; Caroline Poyser²; Paul Dean¹; Aleksandar Demić¹; Alexander Valavanis¹; Dragan Indjin¹; Mohammed Salih¹; Iman Kundu¹; Lianhe Li¹; Andrey Akimov²; Giles Davies¹; Edmund Linfield¹; John Cunningham¹; Anthony Kent^2
1School of Electrical and Electronic Engineering, University of Leeds, United Kingdom; ²School of Physics and Astronomy, University of Nottingham, United Kingdom

We demonstrate a new method for high-speed modulation of terahertz emission and electronic transport of a Ga(Al)As quantum cascade laser using coherent acoustic phonon pulses. The modulation, which is on the order of 6%, can be partially explained by a perturbation-theory analysis. The < 1 ns rise time of the modulation is dominated by parasitic device impedance in our experiment, however, the fast transit of phonons through the QCL heterostructure imply modulation rates > 100 GHz are possible.

11:00-12:30 - We-AM-5 - MMW (active) - Petit Amphi

Chairperson: Chong Han

11:00 We-AM-5-1

Development And Flight Qualification Of The Millimeterwave Receivers For The NASA TROPICS CubeSat Constellation Mission
William Blackwell
MIT Lincoln Laboratory, United States

The Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission was selected by NASA as part of the Earth Venture--Instrument (EVI-3) program and is now in development with planned launch readiness in late 2019. TROPICS comprises a constellation of six CubeSats in three low-Earth low-inclination orbital planes. Each CubeSat will host a high performance millimeterwave radiometer to provide temperature profiles using seven channels near the 118.75 GHz oxygen absorption line, water vapor profiles using three channels near the 183 GHz water vapor absorption line, imagery in a single channel near 90 GHz for precipitation measurements (when combined with higher resolution water vapor channels), and a single channel at 205 GHz that is more sensitive to precipitation-sized ice particles. NEDTs range from approximately 0.5 to 1.0 K for an 8.333 msec integration time.

11:30 We-AM-5-2
High-Power MM-Wave Frequency Multipliers
Oleg Cojocari; Diego Moro-Melgar; Ion Oprea
ACST GmbH, Germany

A novel approach has been developed on monolithic integration of Schottky diodes with CVD diamond substrate for improved thermal dissipation. This allowed development of mm-wave frequency multipliers with unmatched power-handling capability while maintaining state-of-the-art conversion efficiency. This contribution highlights details of this development and summarizes experimental RF-results of high-power multipliers.

11:45 We-AM-5-3
GaAs Schottky Components For 300 GHz Communication Systems Using A Resonator Impedance Matching Approach
Michael Lancaster¹; Cheng Guo¹; Jeff Powell¹; Hui Wang²; Kai Parow-Souchon²; Peter Huggard²; Yi Wang^1
1University of Birmingham, Department of Electronic, Electrical and Systems Engineering, United Kingdom; ²STFC Rutherford Appleton Laboratory, United Kingdom

A interconnection method has been developed to integrate GaAs Schottky diode components with hollow metal waveguides. Instead of using wired or probe impedance matching, an integrated resonator matching circuit has been adopted and a co-design method of active components with waveguide cavity filters developed. The approach transfers most of the matching circuitry from the lossy microstrip to low loss waveguide cavities. It minimises the footprint of the transition and improves the efficiency of the interconnection. This paper reviews the design and test of several building block components for a 300 GHz communications system. A 290-310 GHz single sideband mixer incorporates an integrated waveguide filter to achieve the required image rejection and impedance matching. A 135-150 GHz frequency tripler shows good impedance matching performance with an additional built-in filtering function.

12:00 We-AM-5-4
A 240 GHz Active Multiplier-Based Signal Source For MillimeterWave/Terahertz Applications
Maruf Hossain; Sebastian Boppel; Wolfgang Heinrich; Viktor Krozer
Ferdinand-Braun-Institut, Germany

This paper presents a 240 GHz signal source using a 0.8 Ãfâ?sÃ,µm transferred substrate (TS) InP-HBT technology. The source is based on an active tripler and delivers -3 dBm peak output power at 234 GHz, with a DC consumption of only 50 mW, which corresponds to 0.9 % conversion efficiency. A bandpass filter at the output suppresses all the unwanted harmonics. The tripler achieves more than 50 GHz bandwidth and exhibits very low unwanted harmonics. The core area of the source is only 1.3 x 0.7 mmÃfâ?sÃ,².

12:15 We-AM-5-5
European Schottky-Diode Based Receiver Technology
Oleg Cojocari; Matthias Hoefle; Diego Moro-Melgar; Ion Oprea; Martin Rickes
ACST GmbH, Germany

This contribution summarizes recent achievements of European mm&sub-mm wave receiver technology using Schottky diodes and THz-MICs fabricated by so-called Film-Diode (FD) process. The FD-process has particularly been developed for applications at mm-waves and THz frequencies and targets at ultimate performance at high frequencies. This technology is extensively employed for modern space missions but also finds terrestrial applications.

11:00-12:30 - We-AM-6 - Electronic SC Devices 1 - Room 269

Chairperson: Taiichi Otsuj

11:00 We-AM-6-1

Injection Locking Of Resonant Tunneling Diode Oscillator Using Coherent Terahertz Pulses
Takashi Arikawa¹; Jaeyoung Kim²; Toshikazu Mukai²; Naoki Nishigami³; Masayuki Fujita³; Tadao Nagatsuma³; Koichiro Tanaka^1
1Kyoto University, Japan; ²ROHM Co., Ltd, Japan; ³Osaka university, Japan

We performed injection locking of a resonant tunneling diode (RTD) oscillator using phase-locked picosecond terahertz pulses. We succeeded in coherent sampling of the terahertz electric field emitted from the RTD.

11:30 We-AM-6-2
Intersubband Polaritons In Triple Barrier Resonant Tunneling Diodes
Benedikt Limbacher¹; Martin Kainz¹; Sebastian Schönhuber¹; Moritz Wenclawiak¹; Christian Derntl¹; Hermann Detz²; Aaron Andrews³; Goffried Strasser³; Andreas Schwaighofer³; Bernhard Lendl³; Juraj Darmo¹; Karl Unterrainer^1
1Photonics Institute, TU Wien, Austria; ²CEITEC, Czech Republic; ³TU Wien, Austria

We demonstrate the presence of Intersubband Polaritons in Triple Barrier Resonant Tunneling Diodes. Additionally we investigated the influence of Intersubband Polaritons on the electrical transport and show that the coupling-strength can be modulated electrically.

11:45 We-AM-6-3
Graphene Field-Effect Transistors For Mm-Wave Amplifiers
Andrei Vorobiev¹; Marlene Bonmann¹; Muhammad Asad¹; Xinxin Yang¹; Jan Stake¹; Luca Banszerus²; Christoph Stampfer²; Martin Otto³; Daniel Neumaier^3
1Chalmers University of Technology, Sweden; ²RWTH Aachen University, Germany; ³AMO GmbH, Germany

In this work, we analyze high frequency performance of graphene field-effect transistors (GFETs), applying developed models of drain resistance, carrier velocity and saturation velocity, identify main limitations and propose an approach most promising for further development of the GFETs suitable for advanced mm-wave amplifiers. In particular, it is shown, that the saturation velocity of carriers in the GFETs can be increased up to 5e7 cm/s via encapsulating graphene by hexagonal boron nitride layers, with corresponding increase of extrinsic maximum frequency of oscillation up to 180 GHz at 200 nm gate length

12:00 We-AM-6-4
Wide Bandwidth Terahertz Mixers Based On Graphene FETs
Xinxin Yang¹; Andrei Vorobiev¹; Kjell Jeppson¹; Jan Stake¹; Luca Banszerus²; Christoph Stampfer²; Martin Otto³; Daniel Neumaier^3
1Chalmers University of Technology, Sweden; ²RWTH Aachen University, Germany; ³AMO GmbH, Germany

In this work, resistive fundamental terahertz mixers with wide RF and IF bandwidths based on graphene field-effect transistors have been demonstrated. With an RF frequency range from 220 GHz to 487 GHz, the estimated values of the 3-dB IF bandwidth are 32 GHz and 56 GHz for mixers with GFET gate lengths of 1.2 ?m and 0.6 ?m, respectively. This is competitive with the performance of mixers based on traditional semiconductor technologies.

12:15 We-AM-6-5
Asymmetric Dual Grating Gate Graphene-based THz Detectors
Juan Antonio Delgado Notario¹; Vito Clericò²; Enrique Diez²; Jesus Enrique Velazquez Perez²; Taiichi Otsuji³; Taiichi Otsuji³; Yahya Moubarak Meziani^2
1Tohoku University, Japan; ²University of Salamanca, Spain; ³RIEC (Research Institute of Electrical Communication), Japan

We report on detection of terahertz radiation by using Asymmetric dual grating gates graphene-based FET. The device was fabricated with a stack of h-BN/Graphene/h-BN with a back gate as well as an asymmetric dual grating top gates. It was subjected to terahertz radiation at frequencies of 0.15 and 0.3 THz and a clear photocurrent was obtained.

12:30-14:00 - Lunch

14:00-15:15 Parallel sessions We-PM1

14:00-15:15 - We-PM1-1 - THz Plasma 1 - Room 101

Chairperson: Peter Uhd-Jepsen

14:00 We-PM1-1-1
Terahertz Aqueous Photonics And Beyond
Qi Jin¹; Yiwen E¹; Shenghan Gao¹; Liangliang Zhang²; Cunlin Zhang²; Anton Koroliov³; Sergey Kozlov³; Xi-Cheng Zhang^1
1University of Rochester, United States; ²Capital Normal University, China; ³ITMO University, Russian Federation

THz wave emission from liquids under intense optical excitation provides a new way to generate intense and broadband THz signals. Here, we show that the use of water lines in place of water films as THz emitters to obtain stronger THz signals. In addition, we observe that the polarity of liquid has a significant influence on the THz wave generation. Besides paving the way to develop intense liquid THz sources, our report could be useful for the further study of laser-liquid interaction.

14:30 We-PM1-1-2
Terahertz Wave Generation From Liquid Nitrogen
Alexander Shkurinov
Moscow, Russian Federation

We present the results of research, on the generation of terahertz (THz) radiation under the action of femtosecond laser pulses on liquid nitrogen (LN). Our experimental results supported by theoretical interpretation, showed that under femtosecond laser radiation, liquid and gas emit THz waves in a very different way. We assume that the mobility of ions and electrons in liquid can play an essential role, forming a timedependent quasi static electric field. We discuss the influence of the phase transition of LN from gas to liquid and then to supercritical fluid on the properties of the THz wave generation.

14:45 We-PM1-1-3
Double Pulse Excitation For Enhancing THz Generation In Liquid Jets
Evgenia Ponomareva¹; Sergei Putilin¹; Anastasia Gendrina¹; Semen Smirnov²; Anton Tcypkin¹; Yiwen E³; Sergei Kozlov¹; Xi-Cheng Zhang^3
1ITMO University, Russian Federation; ²Aston University, United Kingdom; ³University of Rochester, United States

We implement a double-pump technique to enhance THz energy generated in liquid jets. The dependence of the THz emission enhancement efficiency on the temporal delay between two collinear optical pulses is experimentally and theoretically investigated. To understand the physics of the process, we compare the cases of 200 fs and 300 fs pump pulses and reveal the advantage of using a pulse of optimal for a specific jet thickness duration for more efficient enhancement. We assume that in addition to the effective method of strong THz generation, double-pump can be a method of measuring the plasma channel lifetime.

15:00 We-PM1-1-4
Flexible Control Of Broadband Terahertz Radiations From Laser Plasmas
Zhelin Zhang¹; Yanping Chen^2
1Tsung-Dao Lee Institute, China; ²Key Laboratory for Laser Plasmas, Shanghai Jiao Tong University, China

Based on theoretical and experimental studies, we demonstrate that the two-color laser scheme in gas plasma can provide effective control of broadband terahertz waves, including their waveforms and polarization states.

14:00-15:15 - We-PM1-2 - PC Devices 2 - Room 162

Chairperson: Masahiro Asada

14:00 We-PM1-2-1

Milliwatt-Class MHz Repetition-Rate THz Source Driven by A Sub-100 Fs High Power Thin-Disk Laser
Frank Meyer; Negar Hekmat; Tim Vogel; Alan Omar; Samira Mansourzadeh; Felix Fobbe; Martin Hoffmann; Yicheng Wang; Clara Saraceno
Ruhr-University Bochum, Germany

We demonstrate optical rectification in GaP crystals driven by a 100 W-class thin-disk oscillator, nonlinearly compressed to sub 100 fs in a multi-pass cell. We measure a power of 1.35 mW, which is the highest average power of a table- top single-cycle THz source at MHz repetition rate so far.

14:30 We-PM1-2-2
Interdigitated Photoconductive Switches For Terahertz Pulses Emission With Electrical Control Of Polarization
Kenneth Maussang¹; Jacques Hawecker²; José Palomo²; Juliette Mangeney²; Sukhdeep S. Dhillon²; Jérôme Tignon^2
1Université de Montpellier, France; ²Laboratoire de Physique de l'ENS - ENS, Université PSL, CNRS, Sorbonne Université, Université Paris, France

Photoconductive switches are widely used for emission and/or detection of terahertz pulses, linearly polarized in a direction fixed by electrodes' geometry. In this work, innovative designs of photoconductive switches are demonstrated and characterized, providing full electrical control on the direction of polarization of the emitted field. Based on an interdigitated scalable geometry, it might be used either for emission or detection, allows fast polarization modulation and polarimetry measurements with a large area receiver. Degree of polarization better than 98% has been measured and investigated numerically. It opens the field of precision terahertz polarimetry.

14:45 We-PM1-2-3
Scalable Large-Area Terahertz Emitters With Improved Electrode Design
Abhishek Singh; Malte Welsch; Stephan Winnerl; Manfred Helm; Harald Schneider
Helmholtz-Zentrum Dresden-Rossendorf, Germany

We have systematically investigated the influence of electrode parameters on the emission efficiency of scalable large-area photoconductive THz emitters. We identify two contributions to THz emission, originating from the photoexcited carriers in the semiconductor and from the interdigitated metal electrodes acting as dipole antennae, respectively. Both contributions are optimized for maximum THz emission efficiency by varying the gap and stripe widths of the interdigitated metal electrodes. Using this approach we achieve a 50% improvement of the radiated THz electric field as compared to electrodes with equal stripe and gap widths.

15:00 We-PM1-2-4
Cavity Based THz Photoconductive Switch: Milliwatt Average Powers
Jacques Hawecker¹; Kenneth Maussang¹; José Palomo¹; Rafaelle Colombelli²; Isabelle Sagnes²; Juliette Mangeney¹; jérome Tignon¹; Sukhdeep Dhillon^1
1Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne University, France; ²Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris Sud, Université Paris-Saclay, C2N M, France

Reaching milliwatt average powers and room temperature operation for THz sources has become the key challenge for the uptake of THz applications that require real-time imaging. This criteria remains extremely challenging. By placing a photoconductive switch within a quasi-resonant cavity, we are able to show average power around 2mW which is an important development towards room temperature THz imaging.

14:00-15:15 - We-PM1-3 - NLO Generation 1 - Amphi Lavoisier

Chairperson: Harmut Roskos

14:00 We-PM1-3-1

Low Noise And High Gain Terahertz Parametric Amplifier
Kosuke Murate; Hikaru Sakai; Yunzhuo Guo; Kodo Kawase
Nagoya University, Japan

In this study, we demonstrated a low-noise, high-gain terahertz (THz) parametric amplifier (TPA). The TPA is divided into two parts: a preamplifier and a main amplifier. In this configuration, wavelength conversion to near-infrared (NIR) light is performed by the preamplifier. The NIR light has different generation angles for each wavelength to satisfy the phase-matching conditions; thus, broadband noise can be spatially removed using an iris. Converting the THz wave again in the main amplifier, an improvement in amplification is realized, while reducing noise. These improvements allowed the amplification gain to reach 98 dB at 506 zJ input at 0.79 THz.

14:30 We-PM1-3-2
Generation Of THz Vortex Beam By Infrared Vector Beam Rectification
Jérôme Degert; Ali Al Dhaybi; Etienne Brasselet; Emmanuel Abraham; Eric Freysz
Université de Bordeaux - LOMA, France

We report on the conversion of an infrared vector beam into THz vortex beams using a ZnTe cubic crystal. We provide a theoretical analysis demonstrating how an infrared vector beam with the azimuthal order l can be transformed into a THz beam endowed with an orbital angular moment content that consists of optical vortices with topological charge +2l or -2l. Experimentally, quasi-monochromatic THz vortex beams with topological charges +2 and -2 are produced and characterized both in amplitude and phase using real-time two-dimensional imaging of the terahertz electric field.

14:45 We-PM1-3-3
Efficient Terahertz Generation And Detection Using CdTe Crystal Pumped By Ultrafast Ytterbium Laser
Xavier Ropagnol¹; Mizuho Matoba²; Joel-Edouard Nkeck³; François Blanchard³; Elchin Isgandarov¹; Junji Yumoto²; Tsuneyuki Ozaki^1
1INRS-EMT, INRS-EMT, Canada; ²The university of Tokyo, Japan; ³ÉTS, Canada

In this work, we study terahertz (THz) generation and detection from CdTe crystal pumped by an Ytterbium (Yb) laser at 1.045 Ã,µm wavelength. We compare the performances of THz emission and detection of CdTe crystals to those of GaP crystals and show 50% higher efficiency for detection and 5 times higher efficiency for generation of THz waves from the CdTe crystal. We demonstrate that the generation process is optical rectification from the bulk crystal while the detection process is based on the Pockel effect. We believe this work shows that CdTe crystal could be used as detector and especially as a source for THz time domain spectroscopy.

15:00 We-PM1-3-4
Evidence For THz Superradiance In Optically-Pumped Quantum-Dot Arrays
W-D. Zhang¹; E. Brown¹; A. Mingardi²; R. Mirin³; N Jahed⁴; D. Saeedkia^4
1Department of Physics, THz labs, Wright State University, United States; ²Departments of Physics and Electrical En, Wright State University, United States; ³Applied Physics Division, National Institute of Standards and Technology, United States; ⁴TeTechS, Canada

We present the first experimental results of THz oscillatory radiation from quantum dot arrays in GaAs pumped by 1550-nm femtosecond pulses. A record of ~117 μW THz power was obtained, with a 1550 nm-to-THz power conversion efficiency of ~0.2%.

14:00-15:15 - We-PM1-4 - QCL 4 - Room 151

Chairperson: Miriam Vitiello

14:00 We-PM1-4-1

Long Wavelength (λ = 10 - 18 μM) Mid-IR Quantum Cascade Lasers Operating In A Continuous Wave At Room Temperature
Roland Teissier; Hadrien Philip; Zeineb Loghmari; Michael Bahriz; Alexei Baranov; Franziska Barho
University of Montpellier, France

We report a study of quantum cascade lasers (QCL), made of InAs and AlSb, operating in the long wavelength mid-infrared range. Lasers based on a design with slightly diagonal intersubband transitions demonstrated improved performances as compared to the previously reported devices employing a vertical scheme. The fabricated lasers operated in the CW regime at 40°C up to a wavelength of 18 μm.

14:30 We-PM1-4-2
Self-starting Harmonic Emission And Active Harmonic Modelocking In THz QCLs
Valentino Pistore¹; Feihu Wang¹; Michael Riesch²; Hanond Nong¹; Pierre-Baptiste Vigneron³; Raffaele Colombelli³; Olivier Parillaud⁴; Christian Jirauschek²; Juliette Mangeney¹; Jerome Tignon¹; Sukhdeep Dhillon^1
1LPENS, France; ²Technical University of Munich, Germany; ³Universite Paris-Sud, France; ⁴III-V Lab, France

In laser technology, harmonic modelocking is usually employed to attain higher repetition rates that is associated with lower noise systems. Despite the favourable dynamics of THz QCLs, harmonic active modelocking has not been experimentally demonstrated yet. In this work, we present the results of active modelocking experiments performed at the fundamental and second harmonic on a 6mm double metal THz QCL. We will also show that in certain cases, QCLs can spontaneously attain second harmonic emission without an active modulation, i.e. self-starting harmonic behaviour.

14:45 We-PM1-4-3
Compact Real-Time Terahertz Spectroscopy Based On Quantum Cascade Lasers
Hua Li; Ziping Li; Wenjian Wan; Kang Zhou; Juncheng Cao
Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, China

We demonstrate the most compact terahertz multiheterodyne dual-comb spectroscopy using two quantum cascade lasers (QCLs) without a need of additional fast detectors. With only ~270 nW terahertz power coupled into a terahertz QCL detector comb (no optics for alignment), the down-converted dual-comb spectra are successfully obtained in real-time at different carrier frequencies. To prove the spectroscopic ability, we further demonstrate that the compact dual-comb system can be used to calibrate the relative humidity in the air and to measure the transmission of samples. Due to the small optical coupling aperture (150 μm), it is also potential to use the dual-comb technique for terahertz imaging.

15:00 We-PM1-4-4
Dynamics Of Optically Mutual-injected Terahertz Quantum Cascade Lasers
Weidong Chu¹; Yuanyuan Li¹; Ning Yang¹; Yan Xie²; Yingxin Wang²; Ziran Zhao²; Jialin Sun²; Lianhe Li^3
1Institute of Applied Physics and Computational Mathematics, China; ²Tsinghua University, China; ³Leeds University, United Kingdom

Based on the rate equation model, we study the phase locking and self-mixing properties of optically mutual-injected terahertz quantum cascade lasers. Within the phase-locked range, the laser array works steadily at the same frequency, and the electric field amplitudes are stable. Outside the phase-locked range, the instantaneous frequencies and electric field amplitudes oscillate with time. When the array works in the phase-locked range, simulation with a moving target shows that self-mixing signals can be observed from each laser.

14:00-15:15 - We-PM1-5 - MMW (passive) - Petit Amphi

Chairperson: Raffaele Colombelli

14:00 We-PM1-5-1

Dual-Band Leaky-Wave Lens Antenna For Submillimeter-Wave Heterodyne Instruments
Sjoerd Bosma¹; Maria Alonso-delPino²; Darwin Blanco¹; Cecile Jung-Kubiak²; Nuria Llombart^1
1Delft University of Technology, Netherlands; ²Jet Propulsion Laboratory, United States

In this contribution, we propose an antenna for a dual-band focal plane array (FPA) heterodyne receiver at 210-240 GHz and 500-580 GHz to perform cometary observations. The proposed antenna is composed of a fused silica lens fed by a leaky wave waveguide feed. The dual-band leaky wave feed is based on a single-layer Frequency Selective Surface (FSS) with a transformer layer which allows to have a quasi-optical system that achieves a footprint of the field of view with overlapped beams and equal beamwidths for both frequency bands. A single pixel antenna prototype is currently being developed.

14:30 We-PM1-5-2
A Compact Butler Matrix Design Based On Metallic Nano Wire Filled Membrane Technology And Tunable Phase Shifter At 160GHz
Dongwei Wang¹; Matthias Jost¹; Matthias Nickel¹; Roland Reese¹; Gustavo Pamplona Rehder²; Serrano Ariana L.C.²; Ferrari Philippe³; Rolf Jakoby¹; Holger Maune^1
1TU Darmstadt, Germany; ²Universidade de São Paulo, Brazil; ³UJF, France

This paper presents the design of a planar miniaturized 4x4 Butler matrix, with implementation of 4 tunable 135° delay line phase shifters for a 160 GHz application. The Butler matrix and phase shifters are both realized with a metallic nanowire filled alumina membrane (NaM) technology, using a slow-wave microstrip line to miniaturize the size and where tunability is achieved by filling in a microwave liquid crystal. Comparing with commonly used corporate feed network, the simulation results show such a Butler matrix with 135°-phase shifters has less insertion loss and reduced size.

14:45 We-PM1-5-3
High Performance On-Chip Array Antenna Based On Metasurface Feeding Structure For Terahertz Integrated Circuits
Mohammad Alibakhshikenari¹; Bal S. Virdee²; Chan H. See³; Raed A. Abd-Alhameed⁴; Ernesto Limiti^5
1Electronic Engineering Department, University of Rome, Italy; ²London Metropolitan University, Center for Communications Technology & Mathematics, School of Computing & Digital Media, United Kingdom; ³Edinburgh Napier University, School of Eng. & the Built Environment, United Kingdom; ⁴University of Bradford, School of Electrical Eng. & Computer Science, United Kingdom; ⁵University of Rome "Tor Vergata", Electronic Engineering Department, Italy

A novel on-chip array antenna with high-performances is investigated which is based on CMOS-20um Silicon technology for operation over 0.6-0.65THz. The proposed array structure is constructed on three layers composed of Silicon-Ground-Silicon layers. Two antennas are implemented on the top layer, where each antenna is constituted from three sub-antennas. The sub-antennas are constructed from interconnected dual-rings. Also, they are interconnected to each other. This approach enlarges the effective aperture area of the array. Surface-waves and substrate losses in the structure are suppressed with via-holes inserted through the three layers and implemented between the radiation elements. To excite the structure, a novel feeding mechanism is used comprising open-circuited microstrip lines, which couple electromagnetic energy from the bottom layer to the antennas through metasurface slot-lines in the middle ground-plane layer. The results show the proposed on-chip antenna array has an average radiation gain, efficiency, and isolation of 7.62dBi, 32.67%, and -30dB, respectively.

15:00 We-PM1-5-4
Microfabrication And Study Of Planar Slow-Wave Structures For Low-Voltage V-band And W-band Vacuum Tubes
Andrey Starodubov¹; Nikita Ryskin¹; Andrey Rozhnev¹; Anton Pavlov²; Alexey Serdobintsev²; Roman Torgashov¹; Victor Galushka¹; Ilya Kozhevnikov²; Igor Bahteev³; Giacomo Ulisse⁴; Viktor Krozer^4
1Saratov Branch, Institute of Radio Engineering and Electronics, RAS, Russian Federation; ²Saratov State University, Russian Federation; ³Central Institute of Measurement Equipment (JSC CIME), Russian Federation; ⁴Goethe University Frankfurt am Main, Germany

We consider further development of our original technology for microfabrication of millimeter-band planar microstrip slow-wave structures (SWS). The technology is based on magnetron sputtering and laser ablation methods. V-band (50-75 GHz) and W-band (75-110 GHz) SWSs are fabricated and characterized by scanning electron and optical microscopy. Electromagnetic parameters of the developed SWSs are studied by numerical simulation and cold-test measurement. We have also carried out preparations and preliminary technological steps for the microfabrication of D-band (110-170 GHz) planar microstrip slow-wave structures.

14:00-15:15 - We-PM1-6 - Microscopy - Room 269

Chairperson: Vincent Wallace

14:00 We-PM1-6-1

Imaging Biological Samples Using Far- And Near-Filed THz Microscopy
Huabin Wang
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, China

Both the far-field and near-field THz imaging techniques have been demonstrated in the detection of biological samples, from which it is reasonable to believe that THz imaging techniques are holding a bright future in biomedical and biological fields.

14:30 We-PM1-6-2
Sub-wavelength THz Imaging Through Optical Rectification
Gizem Soylu¹; Emilie Hérault¹; Fredrik Laurell²; Benoit Boulanger³; Jean-Louis Coutaz^1
1Univ. Grenoble Alpes, Univ. Savoie Mont-Blanc, UMR CNRS 5130, Grenoble INP, IMEP-LAHC, France; ²Department of Applied Physics, KTH, Royal Institute of Technology, Sweden; ³University Grenoble Alpes, Institute Néel, France

Sub-wavelength THz imaging has previously been demonstrated by the optical rectification method, i.e. generating THz waves in the sample [1]. We have rendered the initial experimental setup more practical by using a simple fs laser oscillator and an efficient photo-conducting detector. We thus recorded images, at different THz frequencies with a 41-µm lateral resolution, of a sample made of ZnTe grains, and generated THz peak magnitudes with a 33 µm and 12 µm lateral resolution of a periodically poled KTP crystal.

14:45 We-PM1-6-3
Anisotropic Terahertz Microscopy Of Protein Collective Vibrations: Crystal Symmetry And Hydration Dependence
Jeffrey McKinney; Yanting Deng; Akansha Sharma; Deepu George; Andrea Markelz
Buffalo, United States

A stationary sample anisotropic terahertz microscopy technique is used to characterize the intramolecular vibrations for lysozyme. Tetragonal and triclinic crystals are compared. We find excellent reproducibility within a single crystal symmetry group. Several resonant bands are present for both symmetry groups, indicating they originate with the intramolecular vibrations and not crystal lattice phonons. Bands become more pronounced and higher frequency resonant bands begin to emerge with slight dehydration.

15:00 We-PM1-6-4
Observation Of Bi2Te3/Te Striped Structures Using A Laser Terahertz Emission Microscope
Fumikazu Murakami¹; Kazunori Serita¹; Hironaru Murakami¹; Rea Dalipi¹; Augustine Urbas²; M. Buza³; A. Materna³; Dorota Pawlak³; Masayoshi Tonouchi¹; Iwao Kawayama^1
1Institution of Laser Engineering, Japan; ²Materials and Manufacturing Directorate, United States; ³Institute of Electronic Materials Technology, Poland

We observed waveforms and images of THz radiation from Bi2Te3/Te striped structures with laser terahertz emission microscope (LTEM). The results indicate that THz emission from Te is stronger than from Bi2Te3 and the amplitude of THz with polarization in parallel to the striped lines is larger than that in perpendicular.

15:15-15:45 - Coffee Break

15:45-17:00 Parallel sessions We-PM2

15:45-17:00 - We-PM2-1 - THz Plasma 2 - Room 101

Chairperson: Frank Hegmann

15:45 We-PM2-1-1
Highly Efficient Broadband THz Generation From Mid-IR Laser-Driven Plasma
Claudia Gollner¹; Anastasios D. Koulouklidis²; Valentina Shumakova¹; Vladimir Yu Fedorov³; Audrius Pugzlys¹; Andrius Baltuska¹; Stelios Tzortzakis^4
1Photonics Institute/ TU Wien, Austria; ²Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology - Hellas, Greece; ³P. N. Lebedev Physical Institute of the Russian Academy of Sciences, Russian Federation; ⁴Science Program, Texas A&M University at Qatar, Qatar

We report on THz generation from two-color laser filaments, driven by intense Mid-IR pulses centered at 3.9 µm. We demonstrate generation of THz pulses with a spectral bandwidth of 15 THz, extraordinary conversion efficiency of 2.34% and remarkably high energy of 0.185 mJ.

16:15 We-PM2-1-2
Conical Vs Gaussian Terahertz Emission From Two-Color Laser-Induced Air Plasma Filaments
Christian Sørensen¹; Esben Skovsen²; Jérôme Degert³; Marc Tondusson³; Eric Freysz³; Emmanuel Abraham^3
1Aalborg University, Department of Materials and Production, Denmark; ²Aalborg University, Denmark; ³CNRS LOMA, UMR 5798, Université de Bordeaux, France

We demonstrate that terahertz generation in a two-color laser filament can exhibit conical or Gaussian far-field distribution depending on the experimental conditions. By measuring the spatial distribution of the THz electric field in the 0-3 THz spectral range, we have shown that the conical emission is likely due to photo-induced carriers in the silicon filter used to block the remaining pump laser pulses. However, the terahertz generation can retrieve a Gaussian spatial distribution by replacing the silicon filter by a ceramic one in which the photo-excitation of charge carrier does not occur.

16:30 We-PM2-1-3
Filamentation-assisted MicroJ THz Generation By 2-TW Laser Pulses In A Low-pressure Gas
Maxim Nazarov¹; Alexander Mitrofanov²; Dmitry Sidorov-Biryukov²; Mikhail Chasсhin²; Maxime Bernier³; Alexey Zheltikov⁴; Vladislav Panchenko^2
1NRC "Kurchatov institute", NRC "Kurchatov institute", Russian Federation; ²Kurchatov institute, Russian Federation; ³Institut de Microélectronique, Electromagnétisme et Photonique, IMEP-LAHC (UMR 5130), France; ⁴ILC and Physics Department M.V. Lomonosov Moscow State University, Russian Federation

A 2-TW, 30-fs, 800-nm laser radiation is combined with its second harmonic to yield a two-color filament in a loose-focusing geometry inside a low-pressure gas cell. With multiple filamentation and excessive ionization avoided in our experiments through an appropriate choice of the sort and the pressure of the gas, as well as focusing conditions, this filament provides a bright source of terahertz pulses, at least with microjoule-level, for part of the spectrum below 10 THz. Hundred-fold increase of THz yield is observed for 1-50 mbar gas pressure in comparison with ambient case. This THz output is focusable, as our experiments show, to field intensities high enough to induce a 16% transmission increase of a silicon wafer, indicating THz-field strengths up to 0.3 MV/cm in the beam-waist region.

16:45 We-PM2-1-4
New Approach To THz Pulse Generation In Plasma Created By High-Intensity Laser Field
Anna Bogatskaya; Alexander Popov; Ekaterina Volkova
Moscow State University, Russian Federation

We propose new approach to the problem of generation of terahertz radiation in nonequilibrium plasma channels created by high-intensity laser radiation in gases. Key idea of the proposed approach lies in implementing additional amplification to the laser-induced generated THz pulse due to the specific properties of nonequilibrium plasma channel. We perform a self-consistent analysis of the processes of terahertz pulse formation by four-wave mixing process as well as by relaxation of residual low-frequency currents and it further propagation and amplification in a nonequilibrium plasma medium in a wakefield of the laser pulse. Optimal parameters for the pump laser pulse and gaseous medium are found for the most efficient conversion of its energy into terahertz pulse.

15:45-17:00- We-PM2-2 - Applications 2 - Room 162

Chairperson: Withawat Withayachimnankul

15:45 We-PM2-2-1

Online Measurement Of Tire Ply Balance
Irl Duling; Jeffrey White
TeraMetrix, United States

A critical measurement in the manufacture of tires is the ply balance. This is the amount of rubber above and below the cord. In this talk we will present the online measurement of tire ply balance for both textile and steel cords. A combination of x-ray and nuclear gauges can accomplish this measurement for steel cord, but terahertz is the first technology that can measure balance for textile cord. This is also the first of many possible applications of pulsed terahertz within the tire industry.

16:15 We-PM2-2-2
Highly Integrated Submillimeter-Wave Spectrometer For CubeSats
Goutam Chattopadhyay; Adrian Tang; Maria Alonso-delPino; Cecile Jung-Kubiak; Jacob Kooi; Jose Siles; Choonsup Lee
NASA Jet Propulsion Laboratory, United States

We are developing a highly integrated submillimeter-wave spectrometer suitable for CubeSat and SmallSat platforms. Since the available space and DC power on a CubeSats is limited and the instrument has to be light weight, traditional methods of assembling submillimeter-wave instruments are not suitable on these platforms. In this paper we show how we are addressing all these by using low-profile antennas, MEMS calibration switch, and CMOS spectrometers

16:30 We-PM2-2-3
Investigating The Influence Of A Compact's Geometry On Its Pore Structure And Optical Properties Using Terahertz Spectroscopy
Prince Bawuah¹; Runqiao Dong¹; Mohammed Al-Sharabi¹; Daniel Markl²; Axel Zeitler^1
1University of Cambridge, United Kingdom; ²University of Strathclyde, Institute of Pharmacy and Biomedical, United Kingdom

In this study, terahertz time domain spectroscopy (THz-TDS) is used to analyze how the geometry of a compact affects its pore structure (pore shape and orientation). By using flat-faced and biconvex compacts, it was evident from our analysis that pores tend to assume specific shapes and orientations based on the compact's geometry and this was found to significantly affect the extracted optical properties of samples prepared by mixing a material with polyethylene (PE) or polytetrafluoroethylene (PTFE) ethylene as diluent and subsequent compaction. However, such sensitivity to the pore properties opens a number of industrial applications such as for quality testing of pharmaceutical tablets.

16:45 We-PM2-2-4
On-site Inspection Of Conservation Works Using THz TDS
Kirsti Krügener¹; Jan Ornik²; Maximilian Schneider²; Alexander Jäckel²; Enrique Castro-Camus³; Martin Koch²; Wolfgang Viöl^1
1HAWK University of Applied Sciences and Arts, Germany; ²Philipps-Universität Marburg, Germany; ³Centro de Investigaciones en Óptica, A.C., Mexico

After conservation works were done, we performed on-site THz TDS measurements of Roman paintings on the facade of Roman Imperial Throne Room in Trier and compared them to in-lab studies on mockup samples. Results indicate that an intermediate layer of cyclododecan sublimated.

15:45-17:00 - We-PM2-3 - NLO Generation 2 - Amphi Lavoisier

Chairperson: Jean-François Roux

15:45 We-PM2-3-1

Improving The Efficiency Of Cherenkov-Type Terahertz Generation In LiNbO3 By Using Longer Wavelength Optical Pump
Sergey Bodrov¹; Igor Ilyakov²; Boris Shishkin²; Michael Bakunov^1
1University of Nizhny Novgorod, Russian Federation; ²Institute of Applied Physics of the Russian Academy of Sciences, Russian Federation

Terahertz generation by optical rectification of femtosecond laser pulses in a structure comprising a 40 µm thick LiNbO3 waveguide layer and an output Si prism has been investigated for different (800-2400 nm) central wavelengths of the optical pump. An increase in the optical-to-terahertz conversion efficiency for longer pump wavelengths has been obtained and attributed to higher saturation pump energy. In particular, record high conversion efficiency of 0.6 % has been achieved for µJ-level pump at 2100 nm.

16:15 We-PM2-3-2
Optical-to-THz Frequency Down-Conversion Utilizing Two-Dimensional Plasmons
Soya Manabe; Taiichi Otsuji; Akira Satou
Tohoku University, Japan

We theoretically study the carrier frequency down-conversion from optical signals to terahertz signals utilizing two-dimensional plasmons in an InGaAs-channel high-electron-mobility transistor (InGaAs-HEMT). We demonstrate that the down-conversion can be implemented by the so-called photonic double-mixing functionality in the HEMT utilizing the plasmonic hydrodynamic nonlinearities and that the double-mixing conversion gain can be enhanced by orders of magnitude with help of the plasmon-resonance effect.

16:30 We-PM2-3-3
Photonic Upconversion For THz Radiometry
Gabriel Santamaria Botello; Kerlos Atia Abdalmalak; Daniel Segovia Vargas; Luis Enrique García Muñoz
Universidad Carlos III de Madrid, Spain

We analyze the feasibility of upconverting mm-wave and THz radiation to the optical domain for high sensitivity radiometry with no need of cryogenic operation. The upconversion takes place via electro-optic modulation in high-Q whispering-gallery resonators. Theoretical noise results show that room-temperature upconversion schemes can achieve sensitivity values comparable to those of cooled state-of-the-art mm-wave LNAs provided that photon conversion efficiencies above 1% are accomplished.

16:45 We-PM2-3-4
Efficient Broadband Terahertz Generation From Organic Crystal BNA Using Near Infrared Pump
Hang Zhao¹; Tong Wu²; Yong Tan²; Gunther Steinfeld³; Yan Zhang⁴; Cunlin Zhang⁴; Liangliang Zhang²; Mostafa Shalaby^4
1Beijing Institute of Technology, China; ²Beijing Institute of Technology, China; ³Swiss Terahertz Research-Zurich, Switzerland; ⁴Capital Normal University, China

we have shown that BNA is potentially a suitable THz emitter for intense source upscaling using high energy NIR lasers. The obtained spectral contents extend up to 8 THz and the conversion efficiency is 0.8%. We did not observe saturation of conversion efficiency or effect of nonlinear absorption at the maximum fluence used in our experiment.

15:45-17:00 - We-PM2-4 - FEL 1 - Room 151

Chairperson: John Jelonnek

15:45 We-PM2-4-1

Ultrafast High-Field THz Beamline At X-ray FEL
Nikola Stojanovic; Rui Pan; Ekaterina Zapolnova
Deutsches Elektronen-Synchrotron (DESY), Germany

THz sources at FLASH utilize spent electron beam from an soft X-ray FEL to generate very intense (up to 150µJ), tunable frequency (1-300THz) and ultrafast narrowband (~10%) THz pulses, which are naturally synchronized to soft X-ray pulses. This unique combination allows for wide range of element specific pump-probe experiments in physics, material science and biology. Here we discuss the unique features of the FLASH THz pulses and the accelerator source that bring along a set of challenges in the diagnostics of their key parameters: pulse energy, spectral, temporal and spatial profiles.

16:15 We-PM2-4-2
Powerful Spatially-Extended Cherenkov Masers For Pumping Systems Of Compton FELs
Nikolai Peskov; Edward Abubakirov; Andrey Denisenko; Naum Ginzburg; Andrey Savilov; Alexander Vikharev; Vladislav Zaslavsky
Institute of Applied Physics RAS, Russian Federation

Conception of Compton-type FELs is under development currently at IAP RAS (N.Novgorod). This concept is aimed at reducing energy of a driving relativistic electron beam and thereby increasing efficiency of the electron-wave interaction in FEL, as well as achieving relative compactness of the generator. The basis of this concept is RF-undulators of a new type - the so-called "flying" undulators. The report is devoted to design parameters of the Cherenkov maser intended for powering the RF-undulator of such type in the Ka-band, results of its simulation and initial experimental studies. In order to achieve the required sub-gigawatt power level of the pumping wave in a strongly oversized oscillator, we exploit the original idea of using two-dimensional distributed feedback implemented in the 2D doubly-periodical slow-wave structures.

16:30 We-PM2-4-3
Regime Of Multi-Stage Trapping In Free Electron Lasers
Andrey Savilov; Yulia Oparina; Nikolai Peskov
Institute of Applied Physics RAS, Russian Federation

We describe two different ways of the use of the regime of "multi-stage" trapping in Free-Electron Laser. First, this regime can be a way for efficiency enhancement of FELs operating in the SASE regime. Second, multi-stage amplification of a single-frequency RF signal can lead to an effective cooling of the operating electron beam.

16:45 We-PM2-4-4
Accelerator-based Tunable THz Source For Pump-and-probe Experiments At The European X-ray Free-Electron Laser Facility
Hamed Shaker¹; Mikhail Krasilnikov¹; Prach Boonpornprasert¹; Xiangkun Li¹; Georgi Georgiev¹; Axel Brachmann²; Ye Chen¹; James Good¹; Matthias Gross¹; Holger Huck¹; Igor Isaev¹; Christian Koschitzki¹; Gerald Koss¹; Shankar Lal¹; Osip Lishilin¹; Gregor Loisch¹; David David Melkumyan¹; Raffael Niemczyk¹; Heinz-Dieter Nuhn²; Anne Oppelt¹; Sebastian Philipp¹; Mario Pohl¹; Houjun Qian¹; Evgeny Schneidmiller¹; Guan Shu¹; Joerg Schultze¹; Frank Stephan¹; Grygorii Vashchenko¹; Mikhail Yurkov^1
1DESY, Germany; ²SLAC, United States

There is a high demand for intense THz sources since "many excitation mechanisms of matter resonate in the terahertz regime" especially for condensed matters. "Accelerator-based THz sources provide the wide tunability together with high intensity and repetition rates beyond 100 kHz, that will enable broad application at the European XFEL to the most interesting scientific problems in the field" [1]. Supported by European XFEL a proof of principle study is started at the Photo-Injector Test Facility located at DESY in Zeuthen site (PITZ). Since PITZ and European XFEL electron sources are identical the X-ray and THz radiation can be produced with identical bunch train structure so that for every X-ray pulse a corresponding THz pulse can be provided for the pump-and-probe experiments.

15:45-17:00 - We-PM2-5 - Metamaterials 4 - Petit Amphi

Chairperson: Fritz Keilmann

15:45 We-PM2-5-1

Sensitive Biomolecule Sensing And Imaging Platforms Using Terahertz Metamaterials
Minah Seo; Sang-Hun Lee
Korea Institute of Science and Technology, Republic of Korea

We developed terahertz time-domain sensing and imaging platforms for highly sensitive and selective molecule detection in very low concentration. Highly sensitive sensing performance was obtained by various designs of nanoscale metal resonators and their lateral pattern array. Small quantity of target biomolecules was detectably assisted by resonance behavior and huge terahertz field enhancement at the near-field regime. Further studies with large area metamaterial sensing chips represented great promise as a two-dimensional imaging sensor with high contrast and efficient discrimination.

16:15 We-PM2-5-2
A Polarization Insensitive Metasurface For Terahertz Biosensing Applications
Zheng Zhu; Jun Zhou; Lin Zhou; Yanshun Zheng; Jun Wang
University of Electronic Science and Technology of China, China

In this work, a polarization insensitive metasurface operating at the low-frequency edge of the terahertz (THz) band was designed, simulated, optimized, micro-fabricated, and finally tested by the THz time-domain spectroscopy (TDS) system. The simulation and experimental results agree with each other very well. The conclusions show the advantage of this metasurface for THz biosensing applications.

16:30 We-PM2-5-3
Labyrinth Metasurface-based Devices For High-sensitivity Thin Film Sensing
Irati Jauregui-Lopez¹; Pablo Rodriguez-Ulibarri¹; Aitor Urrutia¹; Sergei A. Kuznetsov²; Miguel Beruete^1
1Universidad Pública de Navarra, Dept. Ing. Eléctrica, Electrónica y de Comunicación. Spain; ²Rzhanov Institute of Semiconductor Physics SB RAS, Russia, Spain

In this work, two labyrinth metasurfaces with inductive and capacitive behavior operating in the range of the Terahertz (THz) are presented. The high concentration of electric field in these structures led to excellent results for the use of the devices as thin-film sensors. Numerical and experimental studies have been carried out, with excellent sensitivity and Figure of Merit (FOM) results enhancing dramatically those found in the literature. Due to its great behavior, the use of these thin-film sensors could be extended to perform biological sensing in the future.

16:45 We-PM2-5-4
Terahertz Sensing Of Methyl Chlorpyrifos Using Carbon Nanotube Metamaterials
Ruiqian Wang; Wendao Xu; Lijuan Xie; Yibin Ying
Zhejiang University, China

The results demonstrate that sensitivity is greatly improved using carbon nanotube terahertz metamaterials, which is lower than the World Health Organization's provisional guideline limit for methyl chlorpyrifos in vegetables.

15:45-17:00 - We-PM2-6 - Near-field 1 - Room 269

Chairperson:

15:45 We-PM2-6-1

Mid-infrared Nano-tomography Of Topological Insulator Surfaces
Fabian Mooshammer¹; Fabian Sandner¹; Markus A. Huber¹; Martin Zizlsperger¹; Helena Weigand¹; Markus Plankl¹; Christian Weyrich²; Martin Lanius²; Joern Kampmeier²; Gregor Mussler²; Detlev Gruetzmacher²; Jessica Boland¹; Tyler L. Cocker³; Rupert Huber^1
1University of Regensburg, Germany; ²Peter Gruenberg Institut 9, Germany; ³Michigan State University, United States

The local dielectric function of a few-nm-thick surface layer on a three-dimensional topological insulator is directly retrieved by mid-infrared nano-tomography and suggests the coexistence of a massive electron gas and the topologically protected surface states.

16:15 We-PM2-6-2
Electrically Tunable THz Near-field Nano-imaging And Spectrum Of Split Graphene Ribbon
Zhuocheng Zhang; Min Hu; Yueying Wang; Tianyu Zhang; Xingxing Xu; Sen Gong; Tao Zhao; Shenggang Liu
University of Electronic Science and Technology of China, China

We demonstrate the THz near-field nano-imaging and spectrum of split graphene ribbon utilizing THz scattering near-field optical microscopy (SNOM). Here, we obtain different near-field imaging when we apply different voltages to the device. Furthermore, we investigate THz near-field and far-field spectrum of this structure. We find that only the near-field signal of split graphene ribbon is tuned electrically, rather than far-field signal. The phenomena reveal the THz near-field and far-field properties of graphene with different Fermi level, which is of great significance to learn characteristics of graphene in THz band.

16:30 We-PM2-6-3
Near-field Spectrum Analysis Of TDS S-SNOM
Yueying Wang; Min Hu; Sen Gong; Shenggang Liu; Zhuocheng Zhang; Tianyu Zhang; Yueying Wang
Terahertz Research Center, School of Electronic Science and Engineering, China

TDS s-SNOM, combining two powerful scientific research tools, has brought out promising capacity at nanoscale. In this work ,by analyzing four physical mechanisms in tip-cantilever-substrate model of TDS s-SNOM and simulating various parameters, we report on how tip-cantilever-substrate model affect near-field spectrum and local field density. Numerical simulation results are in good agreement with current experimental result.Further experiments are still in progress. This is of great significance to the development of TDS s-SNOM.

16:45 We-PM2-6-4
Modified AFM-tip For Infrared And THz Near Field Microscopy
Tahsin Akalin
Lille University, France

Near field microscopy is commonly achieved thanks to the exaltation of the field between a tip and the sample. The free space electromagnetic wave at infrared or THz frequencies is focused in this extremely small area compared to the wavelength. In many cases, the probe is a classical AFM-tip which was not made for this purpose. We present here an original approach in order to optimize the interaction between the impinging electromagnetic wave and the antenna-like probe. As a proof of concept we have modified with FIB (Focused Ion Beam) technique a commercial AFM-tip. The results in terms of resolution are very encouraging.

17:00-18:15 - Poster session We-Po3 - Room 8

We-Po3-1
Terahertz Distributed Amplifiers Based On Nanoscale Vacuum Phototubes
Jun Dai; CunJun Ruan; Min Wang; Tian Miao; Yikun Ding
School of Electronic and Information Engineering, Beihang University, China

A high-speed nanoscale vacuum phototube (NVP) is theoretically studied. A small signal circuit model is proposed to characterize the high-frequency performance of an individual phototube. A traveling wave distributed amplifier (TWDA) based on high-frequency NVPs is demonstrated. And the transmission line model is introduced to analyze the voltage distribution and impedance of the TWDA. Our analysis provides a method for determining the optimum number of NVPs to realize high power TWDAs required in terahertz wireless systems and measurement instruments. I

We-Po3-2
20-vane Unstrapped 8-mm Magnetron Operation In Non-π-type Mode
Kostyantyn Ilyenko
IRE NAS of Ukraine, Ukraine

We report 20-vane-resonator unstrapped 8-mm (37.5 GHz) magnetron under development at IRE NAS of Ukraine. The device is supposed to operate in the "-1" spatial-harmonic. In order to provide better modes separation, a non-π-type mode is chosen as the operating one. Results of numerical modelling and experimental investigations of anode slow wave structure (anode block) for π/2-type mode are presented and discussed.

We-Po3-3
Design And Simulation Of A 0.2-THz Traveling-Wave Tube With Sheet Electron Beam Focused By Reversal Magnetic Filed
Nikita Ryskin¹; Andrey Rozhnev¹; Andrey Ploskih²; Vladimir Titov³; Anton Burtsev⁴; Igor Navrotsky⁴; Aleksei Danilushkin^4
1Saratov Branch, Institute of Radio Engineering and Electronics RAS, Russian Federation; ²Saratov State University, Russian Federation; ³Saint Petersburg Electrotechnical University LETI, Russian Federation; ⁴RPE Almaz, Russian Federation

We study a 0.2-THz traveling-wave tube (TWT) with a grating slow-wave structure (SWS) and sheet electron beam focused by reversal magnetic field. Change in the direction of the guiding magnetic field causes change in the direction of beam curling and can suppress the diocotron instability, which is a main problem for sheet beam focusing. Electron gun with a converging sheet beam is designed and fabricated. Over 100 mA current was measured. The results of small-signal and large-signal TWT gain analysis are presented

We-Po3-4
Compact THz Continuous-Wave Clinotron Oscillators
Alexander Danik¹; Alexander Likhachev¹; Sergey Ponomarenko¹; Sergey Kishko¹; Yurii Kovshov¹; Viktor Zavertanniy¹; Sergey Vlasenko²; Eduard Khutoryan¹; Alexei Kuleshov^1
1O. Ya. Usikov Institute for Radiophysics and Electronics of NAS of Ukraine, Ukraine; ²V. N. Karazin Kharkiv National University, Ukraine

Results of research and development of compact continuous wave clinotrons for THz applications are presented. The dependence of optimal phase shift per slow-wave structure period on the length of the system was investigated in 340 GHz continuous-wave (CW) clinotrons. Obtained experimental results show the maximal output power of 100 mW and electronic frequency tuning in the range from 320 GHz to 380 GHz that is in good agreement with the simulation results.

We-Po3-5
Injection Locking Of Resonant Tunneling Diode Oscillator With A Single-Frequency Terahertz Wave
Tomoki Hiraoka¹; Takashi Arikawa¹; Hiroshi Ito²; Koichiro Tanaka^1
1Department of Physics, Graduate School of Science, Kyoto University, Japan; ²Center for Natural Sciences, Kitasato University, Japan

A resonant tunneling diode oscillator (RTD) has been successfully injection locked to a continuous terahertz (THz) wave. The locking range is about 80 MHz when RTD emission power and injected power are set to 10 µW and 4 µW, respectively. Locking range almost obeys a root-square injected-power dependence which is consistent with the Adler's theory.

We-Po3-6
Multicolor Terahertz Generation Via Spectrum-discretized Smith-Purcell Radiation
Weihao Liu; Yucheng Liu; Zijia Yu; Qika Jia; Yalin Lu
University of Science and Technology of China, China

The multicolor (multi-frequency) terahertz radiation is attractive for tremendous applications. Here we illustrate a set of schemes for multicolor terahertz generation, which uses a free-electron beam to excite an array of sub-groups of gradiently changed subwavelength units. Each unit has specific radiative resonant modes with the resonant frequency depending on structure parameters. Every sub-group has several resonant (radiative) frequencies. The multicolor radiation is obtained when the radiation from all sub-groups of the array constructively interfere via the special Smith-Purcell effect.

We-Po3-7
Experimental Advances In 220 GHz Sheet-Beam Traveling-Wave Tubes
Zhaoyun Duan¹; Shengkun Jiang¹; Guang Yang¹; Tao Tang¹; Zhanliang Wang¹; Huarong Gong¹; Yubin Gong¹; Ye Tang²; Pan Pan²; Jun Cai²; Jinjun Feng^2
1University of Electronic Science and Technology of China, China; ²Beijing Vacuum Electronics Research Institute, China

A 220 GHz sheet-beam Traveling-Wave tube (TWT) with output power 50 W was proposed. For the project, a sheet- beam electron gun with a circular cathode and a periodic cusped magnet-tunable quadrupolar magnet (PCM-TQM) focusing system are designed using the three-dimensional particle simulation software Opera 18R2. The experimental results show that the total current of the sheet-beam electron gun is consistent with the simulated beam current of ~135 mA. In addition, the transmission properties of the T-shape staggered double-grating slow wave structure (SWS) with input and output couplers were measured. The measured data show that there is a good passband within 15 GHz frequency range for the proposed TWT. In the future, the device performance will be reported.

We-Po3-8
Graphene And MoS2 Structures For THz Applications
Ayah Hijazi; Amine El Moutaouakil
UAE University, Department of Electrical Engineering, United Arab Emirates

In this work, we report on the plasmon frequency dependency of Graphene and MoS2 nanoribbon patterns on the angle between the plasmon wave vector and Graphene or MoS2 nanoribbons.

We-Po3-9
Research On 96GHz Sheet-beam EIO
Zhenhua Wu; Jielong Li; Chuanhong Xiao; Min Hu; Jie Qing; Bo Wang; Guanyi Zhang; Peipeng Wang
University of Electronic Science and Technology of China, China

Based on the 96 GHz sheet-beam EIO structure, this paper studies the cold cavity parameters and particle simulation of the structure. The results can provide a theoretical basis for the study of electric vacuum high frequency radiation sources.

We-Po3-10
Formation Of High-density Electron Flows By Electron-optical Systems With Multilayer Field Emitters
Gennadi Sominski; Vyacheslav Sezonov; Sergey Taradaev
Peter the Great St.Petersburg Polytechnic University (SPbPU), Russian Federation

This report presents the latest results of investigations of the operation of electron flow formation systems with multi-layer hafnium - platinum cathodes. The operation of systems for formation of sheet electron flows and systems for the formation of annular in cross section flows was studied. The investigated systems, including 20 pairs of hafnium and platinum layers, worked stably under technical vacuum conditions (10^-7 Torr) and provided extremely large emission current densities up to 300--400 A/cm^2, as well as full currents sufficient to ensure the operation of some type spectroscopic gyrotrons of terahertz and subterahertz range.

We-Po3-11
T-Channel JLFET THz Detector
Michal Zaborowski¹; Daniel Tomaszewski¹; Przemyslaw Zagrajek²; Jacek Marczewski^1
1Institute of Electron Technology, Poland; ²Military University of Technology, Poland

A new type of JLFET based detector is described in the paper. This JLFET is equipped with additional electrode contacting side of the channel (giving T-like shape of the channel). The device offers higher photoresponse and better SNR and NEP than its standard counterpart. The most promising for application is -0.5 V .. 0 V gate voltage range, where 84 dB SNR is noted.

We-Po3-12
A Ka-band Backward-Wave Oscillator With Grating Slow-Wave Structure Developed By A Simplified Approach
Natsumi Ishiguro¹; Yukihiro Soga¹; Keisuke Iwabuchi¹; Tatsuya Otake¹; Masayuki Sato¹; Yuya Ishikawa²; Seitaro Mitsudo²; Mitsuhiro Yoshida^3
1Kanazawa University, Japan; ²University of Fukui, Japan; ³High Energy Accelerator Research Organization, Japan

We have devised a timesaving procedure for developing a Ka-band backward-wave oscillator (BWO) with a simple grating slow-wave structure (SWS). We developed a fast 1D-PIC code in radiation simulation to predict the output power for SWS of any design. In the experiment, we also developed an electron-beam transport system, which permits us to replace SWS without exposing the dispenser cathode to the air; thus, an efficient investigation for various kinds of SWSs has become possible. All the processes for developing the BWO, from a design of a SWS to the radiation experiment, were accomplished over several months. This time-saving development method is suitable for carrying out proof-of-principle experiments with various SWSs aiming at a high power THz BWO. Herein, we demonstrate the proposed approach by developing a 40 GHz BWO with a grating SWS.

We-Po3-13
Generation Of Trains Of Ultrashot Microwave Pulses By Two Coupled W-Band TWTs
Anton Ivanov¹; Maksim Nagornyuk¹; Alexander Smirnov¹; Naum Ginzburg²; Roman Rozental²; Mikhail Vilkov^2
1SPE "Salut", Russian Federation; ²Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

Based on a time-domain model, we demonstrate that a periodic train of pulses can be generated in a system of two coupled W-band TWTs operating in regimes of amplification and saturable absorption, respectively. For saturable absorption the Kompfner dip regime implemented by a proper matching of the tube parameters. According to simulations with the parameters of an experimentally realized TWT, the peak power of generated pulses with a duration of 150 ps can achieve 100Ãf¢ââ?s‰â,¬Â°W.

We-Po3-14
Experimental And Numerical Study Of The 0.4-THz Second-Harmonic Gyrotron With A Complex-Cavity Resonator
Yoshinori Tatematsu¹; Teruo Saito¹; Masafumi Fukunari¹; Yuusuke Yamaguchi¹; Y Maeda¹; T Ogura¹; Maria Melnikova²; Andrey Rozhnev²; Nikita Ryskin²; Ilya Bandurkin^3
1Research Center for Development of Far-Infrared Region, University of Fukui, Japan; ²Saratov Branch, Institute of Radio Engineering and Electronics RAS, Russian Federation; ³Institute of Applied Physics RAS, Russian Federation

Second-harmonic 0.4-THz gyrotron with complex-cavity resonator with TE8,3-TE8,5 mode conversion is studied. Cold-cavity electromagnetic parameters are simulated and start-oscillation current is calculated. The numerical results are compared with the experimental measurements.

We-Po3-15
W-band Pulsed TWT Family With Different Output Power
Anton Ivanov¹; Maksim Nagornyuk¹; Alexander Smirnov¹; Roman Rozental²; Nikolai Peskov^2
1SPE "Salut", SPE "Salut", Russian Federation; ²Institute of Applied Physics RAS, Russian Federation

Results of development and measurement of a series of pulsed TWTs at the W-band are presented. Simulations of the slow-wave and electron-optical systems have been carried out, the manufacturing technology has been developed, and TWTs based on the folded-waveguide slow-wave system have been realized. The measured output power varied from 5 to 50 W with a gain of up to 32 dB and an operation frequency band up to 6%.

We-Po3-16
Time Resolution And Power Dependence Of Transistor Based Terahertz Detectors
Przemyslaw Zagrajek¹; Sergey Danilov²; Jacek Marczewski³; Michal Zaborowski³; Dariusz Obrebski³; Cezary Kolacinski³; Pawel Kopyt⁴; Dmitry But⁵; Wojciech Knap⁵; Sergey Ganichev^6
1Military University of Technology, Poland; ²University of Regensburg, Germany; ³Institute of Electron Technology, Poland; ⁴Warsaw University of Technology, Poland; ⁵Institute of High Pressure Physics, Poland; ⁶University of Regensburg, Germany

We present a systematic study of time resolution and power dependence of the responsivity of three significantly different types of the state-of-the-art plasma based detectors. We analyze photoresponse of custom-made Si junctionless FETs (JLFETs), Si MOSFETs and GaAs-based high electron mobility transistors (HEMT) detectors, which represent structures that are very often employed in experiments dedicated to detection of sub-THz and THz radiation using FETs. All structures have been monolithically integrated with a log-periodic broad-band planar antenna. Time resolved photoresponse of room temperature detectors have been studied applying nanosecond pulses of monochromatic linearly polarized terahertz laser radiation with frequencies f ranging from 0.6 to 3.3 THz. Our measurements demonstrate that these detectors have nanoseconds response time and explore nonlinearity of detectors power dependence for different gate voltages applied to FET transistors

We-Po3-17
Application Of Clinotron Scheme For THz Traveling-Wave-Tubes
Alexander Danik; Alexander Likhachev; Sergey Ponomarenko; Sergey Kishko; Yurii Kovshov; Eduard Khutoryan; Alexei Kuleshov
O. Ya. Usikov Institute for Radiophysics and Electronics of NAS of Ukraine, Ukraine

Results of simulations of the 340 GHz TWT based on the clinotron operation scheme are presented. The advantage of applied clinotron scheme for THz TWT is demonstrated by the results of gain analysis, those were obtained according to non-linear non-stationary theory of the clinotron amplifier. The output power of simulated clinotron-TWT exceeds the power of ordinary TWT.

Results of simulations of the 340 GHz TWT based on the clinotron operation scheme are presented. The advantage of applied clinotron scheme for THz TWT is demonstrated by the results of gain analysis, those were obtained according to non-linear non-stationary theory of the clinotron amplifier. The output power of simulated clinotron-TWT exceeds the power of ordinary TWT.

We-Po3-18
Fmax=800GHz With 75 Nm Gate Length And Asymmetric Gate Recess For InGaAs/InAlAs PHEMT
Sylvain Bollaert; Mohammed Samnouni; Nicholas Wichmann; Xavier Wallart; Christophe Coinon; Sylvie Lepilliet
IEMN, University of Lille - CNRS, France

In this paper, we present a high maximum frequency of oscillation (fmax) and a current-gain cutoff frequency (fT) of 800 GHz and 260 GHz respectively with pseudomorphic high-electron mobility transistor (PHEMT), using a composite, InGaAs/InAs/InGaAs channel and an asymmetric gate recess. This result was achieved with long gate length LG = 75 nm. The noise performance has been explored until 110 GHz, and gives a minimum noise figure NFmin = 0.8 dB (1.8 dB) with associated gain Gass = 16 dB (11.6 dB) at 40 GHz (94 GHz). Moreover extending the drain recess length to 225 nm and reducing the gate to source distance by 200 nm allows a fmax = 1.2 THz.

We-Po3-19
Coherent Terahertz Radiation From Homogeneous Intrinsic Josephson Junction Stacks Of Cuprate High-Temperature Superconductors
Manabu Tsujimoto; Genki Kuwano; Yota Kaneko; Takayuki Imai; Yukino Ono; Shungo Nakagawa; Shinji Kusunose; Takanari Kashiwagi; Hidetoshi Minami; Kazuo Kadowaki
University of Tsukuba, Japan

A stack of intrinsic Josephson junctions of high-temperature superconductors is emerging as compact sources of coherent THz radiation. We present an effective engineering technique for accurately controlling sidewall angles of the mesa structure made of single crystalline Bi2Sr2CaCu2O8+δ. We investigate the effect of homogeneity of stacked junctions on synchronization using two mesas with varying sidewall angels. The radiation intensity can be suppressed significantly when the sidewall is tilted more than ~10%. This finding allows us to construct higher power sources based on superconductors that are able to fill the technological gap in the sub-THz regime.

We-Po3-20
High Performance Surface Plasmon Polaritons From Mediated Coupling Excitation
Sen Gong; Wei Wang; Tao Zhao; Min Hu; Diwei Liu; Zhenhua Wu; Renbin Zhong; Shenggang Liu
University of Electronic Science and Technology of China, China

Graphene surface plasmon polartions (GSPs) opens a promising way for terahertz sources. However, there are still many challenges for the current GSPs electric excitation methods. Here, high performance GSPs from the mediated coupling is presented, which are excited by the coupling between the GSPs in graphene based hyperbolic medium (GHM) and spoof surface plasmons (SSPs) in a designed grating. Compared with current methods, there are many advantages, as low propagation loss, strong coherence, wide tuning bandwidth and large power density. Therefore, this work is of great significance of terahertz radiation sources.

We-Po3-21
On The Effect Of Quantum Capacitance In Graphene FET THz Detectors
Mehdi Hasan; Berardi Sensale-Rodriguez
University of Utah, United States

We analyze the impact of quantum capacitance on the response of graphene-based field effect transistors (FETs) operating as THz detectors. Resulting from its atomically thin body and its particular band structure, the quantum capacitance in graphene has different behavior than that in bulk-semiconductor two-dimensional electron gases. Furthermore, we analyze and identify non-homogeneities and impurities, which in practice lead to a finite minimum effective charge density as well as to a finite minimum conductivity in graphene, as an effect that can degrade the predicted theoretical performance of graphene-based THz devices.

We-Po3-22
Control Of Mesa Sidewalls For Coherent Terahertz Radiation From Intrinsic Josephson Junctions Of High-Tc Superconductors
Genki Kuwano; Yota Kaneko; Takayuki Imai; Yukino Ono; Shungo Nakagawa; Shinji Kusunose; Takanari Kashiwagi; Hidetoshi Minami; Kazuo Kadowaki; Manabu Tsujimoto
University of Tsukuba, Japan

Compact and solid-state CW terahertz sources based on stacks of intrinsic Josephson junctions of high-Tc superconductors are interested in both scientific and industrial fields. In this study, we focus on the effect of the mesa sidewalls associated with variation in characteristics of the stacked junctions. We implement an effective laser lithography to pattern two neighboring mesas with varying sidewall angles on the identical superconducting crystal base. The intense radiation is observed only from the mesas with rather vertical sidewalls, suggesting that the distribution uniformity is a key ingredient to promote the spontaneous synchronization among thousands of intrinsic junctions.

We-Po3-23
A Graphene Self-Switching Diode Bridge Rectifier
Joseph Brownless; Jiawei Zhang; Aimin Song
University of Manchester, United Kingdom

Here we present theory and measurements for a bridge rectifier formed from arrays of graphene self-switching diodes (GSSDs). Graphene's extremely high carrier mobility allows GSSDs to work at THz frequencies, with the bridge rectifier structure allowing for full wave rectification of an AC signal. We derive an equation for the voltage output of a GSSD bridge rectifier, predicting a quadratic dependence on input current. This relationship is confirmed using AC and DC measurements. The fabricated rectifier has a high room temperature intrinsic responsivity of 3,230 V/W at low frequency and a low noise equivalent power of 7.0 pW/Hz^1/2.

 

We-Po3-24
Stokes-parameter Analysis Of Circular Polarized Terahertz Waves From Superconducting Josephson Plasma Emitter
Keiichiro Maeda; Shuma Fujita; Asem Elarabi; Manabu Tsujimoto; Itsuhiro Kakeya
Kyoto University, Japan

We have been studying terahertz sources which consists of intrinsic Josephson junctions of high-Tc superconductors. In this paper, we identify the helicity of terahertz waves emitted from the device of high-Tc superconductors by using a quarter-wave-plate (QWP) of terahertz band. We can observe the right-handed circular polarization from the terahertz source. Moreover, the obtained Stokes parameters are consistent with data of axial ratio measurements without the QWP. We plan to identify the helicity about other positions of current injection.

We-Po3-25
Negative Differential Resistance In ZnO-based Resonant Tunneling Diodes
Vadim Sirkeli¹; Sergiu Vatavu²; Oktay Yilmazoglu¹; Sascha Preu¹; Hans Hartnagel^1
1Technische Universitat Darmstadt, Germany; ²Moldova State University, Republic of Moldova

We present the results of a simulation study of resonant tunneling transport of non-polar m-plane ZnO/ZnMgO quantum structures with double and triple quantum barriers. It is found that in current density-voltage characteristics of such devices a region is present with negative differential resistance and this feature can be used for the generation of terahertz waves. The best performance at room temperature with output power of 912 µW @ 1 THz is derived for the non-polar m-plane ZnO/ZnMgO structures with triple quantum barriers and optimized design.

We-Po3-26
Terahertz Radiation From The High-Tc Superconductor Intrinsic Josephson Junctions Coupled To An External Resonator
Yukino Ono; Hidetoshi Minami; Genki Kuwano; Shinji Kusunose; Takayuki Imai; Yota Kaneko; Shungo Nakagawa; Takanari Kashiwagi; Manabu Tsujimoto; Kazuo Kadowaki
University of Tsukuba, Japan

Continuous and coherent terahertz radiation is emitted from mesa-shaped devices made of the intrinsic Josephson junctions (IJJs) in high-Tc superconductor Bi2Sr2CaCu2O8+ÃfÆ'Ã?â?TÃfâ?¦Ã,½ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,´. In this study, we have for the first time succeeded in separating the functions of resonator and antenna from the IJJs mesa, by miniaturizing the mesa to about 1/70 of the conventional ones and by coupling it to an external patch resonator. We have observed radiation at designed resonant frequencies and directivity of the patch resonator/antenna. The radiation intensity per mesa area is a few times bigger than typical ones of the conventional mesa devices. This result provides us with an effective way to improve the radiation characteristics and extend the radiation frequency.

We-Po3-27
A Scalable Photomixing Array For Increased Emitted Power
Alvaro Pascual-Gracia¹; Mushin Ali²; Luis-Enrique García-Muñoz²; Guillermo Carpintero²; David González-Ovejero¹; Ronan Sauleau¹; Frédéric Van Dijk^3
1IETR, France; ²UC3M, Spain; ³III-V Labs, France

The goal of this work is to increase the emitted power at E band using a photomixing antenna array. The antenna architecture has been selected to yield a scalable design, high efficiency, and bandwidth (> 10%). A first prototype has been tested in a communications link with one active photodiode at a data rate of 2.15 Gb/s and 25 cm distance.

We-Po3-28
Unit-cell Design For Antenna Arrays Efficiently Matched To Uni-travelling-carrier Photodiodes
Alvaro Pascual-Gracia¹; David González-Ovejero¹; Ronan Sauleau¹; Luis-Enrique García-Muñoz^2
1IETR, France; ²UC3M, Spain

We present an antenna array conceived to obtain efficient matching to integrated sources or loads with low input resistance using a backing grid. From an infinite array approach, we derive closed-form expressions for the different elements in the equivalent network representation. This analytic approach enables the preliminary design of arrays with improved matching efficiency for optimum power transmission/reception. A solution matched to a uni-travelling-carrier photodiode is presented with a maximum 3 dB power improvement compared to a 72 ? antenna, featuring 50 % bandwidth.

We-Po3-29
90 GHz Branch-line Coupler On GaN-on-Low Resistivity Silicon For MMIC Technology
Bhavana Benakaprasad¹; Abdalla Eblabla¹; Xu Li²; Khaled Elgaid^1
1Cardiff University, United Kingdom; ²Glasgow University, Nanotechnology, United Kingdom

We demonstrate a quadrature branch-line coupler operating at 90 GHz on GaN-on-low resistivity silicon substrates (ρ < 40 â"¦.cm). To reduce the losses offered by the low-resistivity silicon at 90 GHz, a shielding technique is used where the silicon substrate is covered by ground plane (Al metal). SiO2 dielectric of thickness 10 µm is used as a spacer between the top metal and ground plane to further improve the performance of the coupler. Measured results showed return loss and isolation as low as -25 dB and -16 dB respectively, and coupling loss of -4 ± 0.5 dB from 81 GHz to 101 GHz. The output amplitude imbalance achieved was less than 5 dB. The coupler validates the shielding MMIC technology on GaN-on-low resistivity silicon substrate.

We-Po3-30
The Effect Of Phosphor Coating On THz/mm Wave-Plasma Interaction In Glow Discharge Detector
Cemre Kusoglu Sarikaya; Demiral Akbar; Hakan Altan
Middle East Technical University, Department of Physics, Turkey

Glow discharge detectors (GDDs) attract attention because they have advantageous features compared to commercial detectors currently used for detecting THz and mm waves. Studies in the literature show that N523-coded GDD which has a phosphorous coating exhibits the best performance. However, to the best of our knowledge, no study has been carried out yet to demonstrate the effect of phosphorus coating on the detection mechanism. Therefore, in this study, it is aimed to understand this effect by simulating the plasma consisting of Ne-Xe mixture in N523 coded GDD with the parallel 1d3v Particle in Cell/Monte Carlo Collision (PIC/MCC) code.

We-Po3-31
Z-Shaped Dual Band Circular Polarized Microstrip Antenna For THz Communication
Shahid Ullah; CunJun Ruan; Tanveer Ul Haq
School of Electronic and Information Engineering, Beihang University, China

In this paper a simple z-shaped dual band circular polarized (CP) terahertz (THz) monopole antenna is designed for short range communication applications. Circular polarization is obtained by rotating the z-shape radiating element by 450 around the horizontal plane with microstrip line. The antenna is operating at dual band with bandwidth of 50 GHz (0.19-0.24 THz) and 340 GHz (0.27-0.61THz). It has a left hand circular polarized (LHCP) antenna having below 3dB axial ratio with bandwidth of 110 GHz (0.38-0.49 THz) and 15 GHz (0.575-0.59 THz). The total dimension of the antenna is 850ÃfÆ'Ã?â?TÃfâ? Ã¢â,¬â"¢ÃfÆ'Ã,¢Ãf¢ââ,¬Å¡Ã,¬"770ÃfÆ'Ã?â?TÃfâ? Ã¢â,¬â"¢ÃfÆ'Ã,¢Ãf¢ââ,¬Å¡Ã,¬"197 ÃfÆ'Ã?â?TÃfâ?¦Ã,½ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,¼m3

We-Po3-32
A Schottky Diode Multiplier Chain Based On Three-dimensional Stacking Integration At 410GHz To 510GHz
Jun Jiang¹; Chen Peng¹; He Yue¹; Li Li¹; Tian Yaoling¹; Hao Hailong^2
1Microsystem and Terahertz Research Center (MTRC), CAEP, China; ²IEE, CAEP, China

The research introduced the integration technology of three-Dimensional stacked terahertz transmitter link based on schottky diode multiplier at 410GHz to 510GHz. In the multiplier chain, there are five stages: the E-band multiplier, E band drive amplifier, D-band doubler and antenna. Firstly, the five different parts have been designed separately. Secondly, the different stage has been designed onto different layers, and the transmission direction has been changed to vertical direction from horizontal direction. Finally, the 3D stacked terahertz transmitter has been finished, and it is smaller than the separate modules with the similarly results. The final size changed from 110mm to 13mm, and the performance is similar to the chain based on discrete modulesï¼Å'which is better than 50uW.

We-Po3-33
A 410-510GHz Room Temperature Local Oscillation Source For SIS Mixers
Peng Chen¹; Li Li¹; Kun Huang¹; Shengcai Shi²; Kun Zhang^2
1Microsystem and Terahertz Research Center, China Academy of Engineering Physics, China; ²Purple Mountain Observatory, China

A 410-510GHz local oscillation source for SIS mixers has been designed, fabricated, and tested. The source is a Ã- 24 frequency multiplier working at room temperature. It converts the input low band microwave signals to submillimeter signals. It is comprised of an E band quadrupler, a bandpass filter, a power amplifier, a D band doubler and a final trippler. Both of the D band doubler and the final trippler use plannar Schottky diodes and quartz based circuits to realize frequency multiplication. Over the 410-510GHz band, the output power of the source is above 50uW, and the maximum is 122uW in 461.8GHz. A horn antenna is connected with the source to radiate the power to SIS mixers which are used for submillimeter radio telescope in Purple Mountain Observatory in China.

We-Po3-34
Dielectric Rod Antenna Array For Photonic-Based Sub-Terahertz Beamforming
Serguei Smirnov¹; Alvaro Morales²; Chigo Okonkwo²; Idelfonso Tafur Monroy²; Dmitri V. Lioubtchenko¹; Joachim Oberhammer^1
1KTH Royal Institute of Technology, Sweden; ²Eindhoven University of Technology, Netherlands

This work presents a dielectric rod antenna array designed for a photonic-enabled beamforming system at sub-terahertz frequencies. The photonic chip generates an optical time delay, providing the beam-steering capability. The antenna array is fabricated from high-resistivity silicon by micro-machining. Simulation results demonstrate a directivity of 14.7 dBi and a beam steering range of 56 degrees at 85 GHz. The system is intended as a sub-THz transmitter for broadband wireless communications.

We-Po3-35
Graphene Microfabrication For Developing Mm-wave And THz Devices
Andrew Squires; Michael Seo; Simon Lam; Xiang Gao; Ting Zhang; Zhaojun Han; Jia Du
CSIRO, Australia

This paper investigates the microfabrication process of graphene in developing high frequency, particularly millimeter-wave and terahertz, electronic devices. We consider graphene production, transfer, fabrication and electrical characterization. Preliminary results reveal key insights including the benefit of polymer removal in transferring graphene to substrates as well as identifying Ar ion beam etching as being effective in patterning graphene thin films. This work lays a solid foundation in developing a holistic and reliable method to pattern graphene for use in high frequency electronics components.

We-Po3-36
Design, Fabrication And Measurement A Promising Photonic Crystal-like Structure Inside A Rectangular Waveguide
Andrey Starodubov; Artem Badarin; Semen Kurkin; Anton Pavlov; Victor Galushka; Yurii Kalinin; Alexey Koronovskii
Saratov State University, Russian Federation

Experimental and numerical studies of an electrodynamic structure assembled according to photonic crystals' principles placed inside the X-band rectangular waveguide are considered. Such structures are promising for microwave electronics (vircators, FELs, and etc.). Efficient excitation of high-order (and, hence, high-frequency) electromagnetic modes is one the most valuable features of dispersion characteristics of photonic crystal-like structures. The proposed electrodynamic structure is a 2D array of thin metal pins. Transmission and reflection characteristics of the proposed structure were measured experimentally and evaluated numerically in K, Ka and Q bands. The experimental results are in good agreement with the numerical ones.

We-Po3-37
Via-less Microstrip To Rectangular Waveguide Transition On InP
Bilal Hussain¹; Giovanni Serafino²; Paolo Ghelfi²; Antonella Bogoni³; Andreas Stöhr^4
1Suola Superiore Sant'Anna, Italy; ²CNIT, Italy; ³Scoula Superiore Sant' Anna, Italy; ⁴University of Duisburg Essen, Department of Optoelectronics, Germany

Indium-Phosphide (InP) is one of the most common materials used for realizing active devices working in the millimeter frequency range. The isotropic etching profile of InP substrates limits the realization of passive devices, thus requiring an expensive and lossy hybrid platform. This paper presents a via-less, cost-effective and efficient solution for InP substrate. By using the proposed planar solution, it is demonstrated that rectangular waveguides can be realized on InP by fabricating a bed of nail structure which acts as a reflecting boundary for an impinging millimeter wave. As a proof of concept, a transition from microstrip to rectangular waveguide structure is realized within H-band (220-320 GHz) with a return loss of -18dB over a bandwidth of 30 GHz.

We-Po3-38
Schottky Diode Based 220GHz Receivers Operating At Room-Temperature For Passive Security Scanning
Haifan Hu; Xuming Ma
Department of Engineering Physics/ Tsinghua University, China

The designed and fabricated of a 200~240GHz receiver for use with THz radiometers is presented. The receiver is based on a sub-harmonic mixer developed by GaAs Schottky diode, its conversion losses of single sideband (SSB) are 7~12 dB, and it requires 5mW local oscillator (LO) power, which is driven by a 110GHz tripler with about 4% efficiency over the band 105~118GHz, and the maximum efficiency of 5.5% output power has been measured at 108.6GHz.

We-Po3-39
Silicon Based Diode Noise Source Scaling For Noise Measurement Up To 325 GHz
Haitham Ghanem¹; Joao Carlos Azevedo Gonçalves²; Sylvie Lépilliet¹; Daniel Gloria²; Christophe Gaquiere¹; François Danneville¹; Guillaume Ducournau^1
1IEMN, CNRS UMR 8520, France; ²STMicroelectronics, France

In this article, we investigate the use of silicon-based diode for millimeter-wave noise generation. A test bench setup was characterized to perform broadband noise measurements up to 325 GHz. A noise receiver is assembled and its Noise Figure (NF) was extracted using cryogenic Hot/Cold measurements. A unitravelling carrier photodiode (UTC-PD) is used as a noise source and the Excess Noise Ratio (ENR) is extracted using the Y-method, and used as a reference for 300 GHz noise generation. The ENR value of the UTC-PD is to be compared to that of a silicon based integrated diode noise source, which will be tested to perform noise measurements up to 325 GHz.

We-Po3-40
Application Of Sub-THz Circular Dichroism Quasi-Optics To Probe The Conformality Of Solvated Protein
Jhih-Hong Cheng¹; Robert Jones¹; Oleksandr Sushko²; Bin Yang³; Yumiko Tashiro¹; Robert Donnan^1
1Queen Mary University of London, United Kingdom; ²Igor Sikorsky Kyiv Polytechnic Institute, Ukraine; ³University of Chester, United Kingdom

A sub-terahertz (sub-THz) Circular Dichroism (CD) quasi-optical (QO) system has shown utility in acquiring electromagnetic absorption signatures of solvated protein samples over H-band frequencies (220 -- 325 GHz). We report the sub-THz CD signature of Myoglobin in particular. Spectra are reproducible within experimental error

We-Po3-41
Research And Design Of W-Band Waveguide Mode Generator
Lanyue Qi; Xinjian Niu; Jinhao Li; Jianwei Liu
University of Electronic Science and Technology of China, China

In this paper, the research of W-band TE62 coaxial mode generator is studied in detail, and the purity of the mode is improved by selecting a complex coaxial cavity. In order to improve the ability to suppress the unwanted mode, the optimized three-stage smooth coaxial cavity has been used. based on the method of the surface impedance matching theory, the resonant cavity was designed and optimized using the code writing by MATLAB program. Finally, the commercial electromagnetic simulation software is used for verification. The simulation result shows that the purity of the mode exciter is 96.80% when the resonant frequency is 94.12 GHz.

We-Po3-42
A 240 GHz Receiver With 6 Gb/s Data Rate Based On Plasma Wave Detection In SiGe Technology
Kefei Wu¹; Guillaume Ducournau²; Mona Hella^1
1Rensselaer Polytechnic Institute, United States; ²University of Lille, France

This paper presents a fully integrated 240 GHz plasma-wave Field Effect Transistor (FET) direct-detector receiver, implemented in 130 nm Silicon Germanium (SiGe) technology(fT =fmax = 210/250 GHz). The receiver chain is formed of an on-chip patch antenna, plasma-wave detector, and a broadband amplifier. The low modulation frequency characterization shows a responsivity of 15 V/W at 240 GHz, with a drain bias current of 2 µA. The responsivity is higher than 10 V/W from 225 GHz to 250 GHz. When measured with modulated signals at a carrier frequency of 240 GHz, the detected signal shows a clear eye diagram at a data rate up to 6 Gb/s with a bit error rate less than 10E-5.

We-Po3-43
Tunable Notch Filter For Measurements Of Rogue Waves In Gyrotrons
Anton Gashturi¹; Mikhail Goykhman¹; Alexander Gromov¹; Sergey Filchenkov¹; Alexey Palitsin¹; Alexander Panin²; Yuri Rodin²; Roman Rozental²; Nikolai Peskov^1
1Institute of Applied Physics RAS, Russian Federation; ²Institute of Physics of Microstructures RAS, Russian Federation

A novel design of notch filter was proposed and tested. Waveguide filter consists of a prismatic resonator coupled to waveguide by a slot and a frequency tuning plunger. We intend to apply this filter for measuring the output radiation of Ka-band gyrotron operating in regime of rogue wave generation and for microwave plasma diagnostics. X-band prototype of the filter was manufactured and its characteristics were measured.

We-Po3-44
A 3D Printed Waffle Type Waveguide For Millimeter Wave Application
Kenji Itagaki¹; Motonori Doi²; Toru Hara³; Sang-Seok Lee^3
1Tottori Univeristy, Japan; ²Osaka Electro-Communication University, Japan; ³Tottori University, Japan

In this paper, we report a 3D printed waffle type waveguide for millimeter wave application. The waveguide consists of a waveguide part and two filter parts for electromagnetic wave transmission and attenuation, respectively. We fabricated the waveguide using a selective laser sintering metallic 3D printing technique, and achieved smaller reflection loss than -20 dB and low insertion loss from 22.3 GHz to 34.0 GHz.

We-Po3-45
Impedance Matching Networks Designed By Evolutionary Algorithms
Vanessa Fenlon; James McCubbin; Claudio Balocco
Durham University, Engineering Department, United Kingdom

A key challenge to extend the operation of electronics nanodevices to mm-wave and THz frequencies is the large impedance mismatch among all components. Here we propose a methodology based on a genetic algorithm coupled to a 3D electromagnetic simulator for designing compact matching networks suitable for operation up to THz frequencies. Both narrow and broad band networks can be realized with the same approach, simply by changing to a suitable fitness function. Structures showing a theoretical voltage standing-wave ratio below 1.03 were obtained for a narrow band circuit centered at 1 THz and below 1.29 in the range 0.95-1.15 THz with a load impedance of 1 kΩ.

We-Po3-46
Millimeter-wave-triggering Of Insulator-to-metal Transition In Vanadium Dioxide
Fatemeh Qaderi¹; Andrei Muller¹; Anna Krammer¹; Miroslav Veljovic¹; Zoltan Ollmann²; Mozhgan Hayati²; Anja Skrivervik¹; Andreas Schueler¹; Thomas Feurer²; Adrian Ionescu^1
1Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland; ²University of Bern, University of Bern, Hochschulstrasse 6, Bern, Switzerland
We establish insulator-to-metal transition (IMT) in Vanadium dioxide (VO2) by millimeter-wave (mm-wave) actuation, using two coupled dipole antennas: a simple one as a continuous mm-wave-source and the other one with an embedded VO2 part as an absorber. We measured |S12| by a vector network analyzer (VNA), to show how the induced mm-wave power in insulating biased VO2 causes IMT. The bias voltage is set to enhance the sensitivity in VO2. The VO2 embedded antenna shows sensitivity to the mm-wave power down to 3.2 μW. The experiment proves the detection concept also for terahertz frequencies.

We-Po3-47
A 0.13 THz Amplifier Integrated With A Frequency Doubler For A 0.26 THz 0 DBm Output Power
Hao Gao¹; Jixin Chen²; Wei Hong²; Peter Baltus^1
1Eindhoven University of Technology, Netherlands; ²Southeast University, China

This contribution presents a 0.26 THz power unit in a 0.13 Ã,µm SiGe BiCMOS technology. This submillimeter-wave frequency power unit is composed of a 2-stage 0.13 THz amplifier integrated together with a 1-stage frequency doubler. In an active submillimeter-wave frequency array, the size of the power unit is critical. In this work, a compact power unit is achieved through on-chip broadside transformers. With this compact solution, the area of the core part of this power unit is 110*900Ã,µm2 and the output power at 0.26 THz is 0 dBm.

We-Po3-48
Comparison Of Fourth-harmonic And Combined Doubler/Subharmonic Mixer With Integrated MMIC Based Local Oscillator
Jose M. Pérez-Escudero; Carlos Quemada; Iñigo Ederra; Ramón Gonzalo
Public University of Navarra, Spain

In this paper a comparison between a fourth harmonic mixer and a combined doubler/subharmonic mixer based on Schottky diodes working at 300 GHz with MMIC Local Oscillator (LO) integrated in single enclosing is presented. Both configurations allow reducing the LO requirements, since a lower LO frequency is used. In addition, the integration of the MMIC Local Oscillator with the mixer in the same single metallic block allows avoiding flange connections. This way, misalignment errors are also prevented. In addition, the compactness of this solution is also remarkable, leading to a significant weight reduction.

We-Po3-49
Long-Distance Coherent Signal Transmission And Reception Of Optically-Connected 96 GHz Millimeter-Wave Radar System For Runway Foreign Object Debris Detection
Shunichi Futatsumori; Kazuyuki Morioka; Akiko Kohmura; Naruto Yonemoto
Electronic Navigation Research Institute, Japan

To detect the small foreign object debris (FOD) on the airport runway, the FOD detection system based on the optically-connected 96 GHz distributed-type millimeter-wave radar have been developed. In this paper, long-distance coherent signal transmission and reception for Radio-over-Fiber (RoF) based radar system are discussed. The coherent signal network based on optical wavelength division multiplexers. In addition, the radar transmission signal and the receiving signal are transferred by the millimeter-wave RoF and 10 gigabit Ethernet, respectively.

We-Po3-50
Performance Characterization Method Of Broadband Terahertz Video Cameras
Vishal Jagtap; Robin Zatta; Janusz Grzyb; Ullrich Pfeiffer
Institute for High Frequency & Communication Technology, Germany

Integrated THz systems comprising index matched optical media introduce discontinuities in the propagation path leading to an etaloning effect. The etaloning hinders the absolute accuracy of a measuring instrument thereby limiting its applicability. A methodology using computational notch filtering is implemented here to extract the true performance of a measuring instrument. Specifically, the responsivity and NEP of the portable room temperature 1k-pixel terahertz CMOS camera have been investigated using a continuously tunable broadband spectrally pure terahertz photomixer source. Applying methodology revealed a peak responsivity of 20 MV/W at 822 GHz with a 6-dB bandwidth of 265 GHz and a minimum integrated NEP of 2.9 nW with 1024 frames averaging at 30fps.

We-Po3-51
Laser-Driven Semiconductor Switch As A Diagnostic Method In Terahertz Band
Maxim Kulygin
Institute of Applied Physics, Russian Federation

A conception of using a laser-driven resonator cavity switch as a diagnostic method for semiconductors in terahertz frequency band is presented. The resonant behavior allows one to achieve good accuracy in measuring the semiconductor's permittivity and loss tangent. The method features extremely low amount of semiconductor needed for the analysis in comparison with known methods.

We-Po3-52
THz Conductivity In Metal Organic Frameworks (MOF)
Jens Neu; Brian Pattengale; Jacob A. Spies; Sarah Ostresh; Uriel Tayvah; Chalres A. Schmuttenmaer
Yale University, United States

Metal organic frameworks (MOFs) are an emerging class of materials. These materials exhibit a large degree of porosity resulting in a low density. These are promising attributes for the fabrication of low-weight and wearable electronics. In this submission, an electrically conductive MOF is investigated. We present temperature-resolved THz-TDS measurements, OPTP, and TRTS measurements. We detected several low energy vibrational excitations in the TDS traces, as well as photoconductivity in the OPTP and TRTS. These measurements provide a pathway to explain the underlying processes of conductivity in this material system.

We-Po3-53
Broadband Characterization Of Glass And Polymer Materials Using THz-TDS
MD SAIFUL ISLAM¹; Jakeya Sultana¹; Cristiano. M. B Cordeiro²; A. L. S Cruz³; Alex Dinovitser⁴; Brian W.-H Ng⁴; Derek Abbott^4
1The University of Adelaide, Australia; ²The University of Adelaide, IPAS, Australia; ³Braz Cubas University, Brazil; ⁴The University of Adelaide, EEE, Australia

The optical properties of polymers and glasses of interests are experimentally characterized using terahertz time domain spectroscopy (THz-TDS). Transmission spectroscopy are used to extract the dielectric properties of Topas (cyclic olefin co-polymer), Zeonex (Cyclo-olefin polymer), Polytetrafluoroethylene (Teflon), high-density polyethylene (HDPE), Polymethyl methacrylate (PMMA), Silica, BK7, Duran and UV-Resin in the terahertz band.

We-Po3-54
Optical Properties Of Polymers In THz Regime And Their Discrimination
Muhammad Mumtaz¹; M. Ahsan Mahmood²; Sabih D Khan³; M. Aslam Zia³; Mushtaq Ahmed³; Izhar Ahmad^3
1National Institute of Lasers & Optronics, Pakistan; ²Pakistan Institute of Engineering and Applied Sciences, Pakistan; ³National Institute of Lasers and Optronics (NILOP), Pakistan

A scheme for the discrimination of different types of polymers using Terahertz time domain spectroscopy (THz-TDS) along-with chemometrics has been presented. Moreover, this work has been extended for the measurement of temperature-dependent optical properties of these polymers and extraction of coefficients of Sellmeier Equation.

We-Po3-55
Multifunctional Graphitic Thin Films For Terahertz Range
Tommi Kaplas¹; Ignas Nevinskas¹; Andrzej Urbanowicz¹; Petr Obraztsov²; Alesia Paddubskaja³; Marian Baah⁴; Irmantas Kasalynas^1
1Center for Physical Sciences and Technology, Lithuania; ²A. M. Prokhorov General Physics Institute, Russian Federation; ³Institute for Nuclear Problems of Belarusian State University, Belarus; ⁴University of Eastern Finland, Finland

Tunability of optical properties of the thin graphitic films (GRFs) makes them versatile for ultra-wide spectral range optics, including terahertz (THz) and microwave optics. Here we report THz properties of a GRF material synthetized directly on a dielectric substrate. Our GRF samples demonstrated about 50 % absorption at VIS-IR and ~15 % absorption at THz (0.5-1.5 THz range). Transmittance of THz waves through the sample could be modulated by absorption of free-carriers induced in the GRF by applied voltage and photo-excitation. Therefore, the reported GRF material shows great potential for electrical/optical modulation of THz and microwave range photonics.

We-Po3-56
Absorption Properties Of 3D-printing MWCNT Composites At The THz Frequency Range
Alexander Badin; Kseniya Simonova; Grigorii Kuleshov; Valentin Suslyaev; Grigorii Dunaevskii; Kirill Dorozhkin; Diana Pidotova; Dmitriy Bodazhkov
National Research Tomsk State University, Russian Federation

Currently, the main method of ensuring electromagnetic compatibility in terms of resistance to the effects of an electromagnetic field, as well as compliance with the requirements for the level of radiated interference, is electromagnetic shielding. Special structures and various materials are used for shielding electromagnetic fields. Among these materials, multi-walled carbon nanotubes (MWCNTs) occupy a special place. MWCNTs are distinguished by their ease, and they are also electrically conductive. In combination with modern additive technologies, such as 3D printing, it is possible to create surfaces of complex geometry with the absorbing properties of electromagnetic radiation in a wide frequency range, including THz. Thus, it is of interest to research the absorbing properties of a material based on dielectric matrix of acrylonitrile-butadiene styrene (ABS) and MWCNTs obtained by additive technology. In paper results of research of absorption properties of 3D-printing MWCNT composites at the 115-258 GHz frequency range are presented.

We-Po3-57
Insulator-metal Transition In PrYCaCoO3 Thin Films Studied By Terahertz and Infrared Spectroscopies
Christelle Kadlec¹; Karel Knizek¹; Jiri Hejtmanek¹; Veronika Goian¹; Josef Bursik²; Miroslav Soroka²; Hynek Nemec^1
1Institute of Physics CAS v.v.i., Czech Republic; ²Institute of Inorganic Chemistry CAS v.v.i., Czech Republic

Charge transport in PrYCaCoO3 thin films was studied experimentally by terahertz (THz) and infrared spectroscopies and by dc conductivity measurements. The metal-insulator transition is clearly visible in THz conductivity, whereas the observed weak temperature dependence of dc conductivity is limited by inter- grain charge transport.

We-Po3-58
Including The Effects Of Covering Layers In The Determination Of Graphene Conductivity From THz-TDS Measurements
Daniel Stock; Christoph Suessmeier; Peter Haring Bolívar
University of Siegen - High Frequency and Quantum Electronics, Germany

We investigate the effects of covering layers on the determination of graphene conductivity from THz-TDS measurements. Especially the errors arising from the common approach to neglect those layers in the determination process are addressed. To counteract those errors an expanded determination method, based on the classical thin-film approach is introduced.

We-Po3-59
THz Properties Of Fe And Ti Oxides Nanoparticles Obtained By Pulsed Laser Ablation
Dmitry M. Ezhov¹; Nazar A. Nikolaev²; Alexander A. Mamrashev²; Valery A. Svetlichnyi¹; Victor N. Cherepanov^1
1Tomsk State University, Russian Federation; ²Institute of Automation and Electrometry SB RAS, Russian Federation

We present Dielectric properties of Fe and Ti oxides nanoparticles (NPs) measured by THz-TDS. The NPs were obtained via ns pulsed laser ablation (PLA) of the metals in air and water and were annealed at different temperatures. We report here the dependence of absorption spectra on NPs structure: from magnetite to hematite for Fe, and from anatase to rutile for Ti. The prospects for their use as materials for the THz photonics are discussed.

We-Po3-60
Terahertz Proton Motions In Proton-Conducting Electrolyte Of Solid Oxide Fuel Cell
Hikaru Takehara¹; Tomohide Morimoto¹; Masaya Nagai¹; Masaaki Ashida¹; Yuji Okuyama²; Yukimune Kani^3
1Osaka University, Japan; ²University of Miyazaki, Japan; ³Panasonic Corporation, Japan

proton conductor has attracted us as a solid electrolyte of the next generation solid oxide fuel cell with high energy conversion efficiency. Doped BaZrO3 perovskite is one of the most promising solid electrolytes with high proton conductivity. Long-range kinetics of protons in doped BaZrO3 have been investigated through low-frequency impedance measurement, diffusion coefficient measurement, NMR measurement. In this report, we demonstrate that THz conductivity measurement is a powerful tool for investigating the picosecond proton dynamics in proton-conducting electrolyte of solid oxide fuel cell. We measure the THz conductivity in the protonconducting solid electrolyte, BaZr0.8Y0.2O3, with THz time-domain spectroscopy at high temperature. Observed sub-THz conductivity reflects the breaking and reforming hydrogen bonding, which is related to the proton hopping between neighboring oxygen atoms. Our results will open a new application of THz spectroscopy for direct characterization of the proton dynamics in solid electrolyte of fuel cell.

We-Po3-61
Optimization Of Terahertz Wave Generation From Nonlinear Optical Crystal Using Amorphous Fluoropolymer Coating
Keisuke Matsumura¹; Yudai Ikegami¹; Peibin Wang¹; Hirohisa Uchida¹; Chisa Koyama²; Takeshi Takagi²; Kei Takeya¹; Kodo Kawase^1
1Nagoya University, Japan; ²ARKRAY Inc., Japan

The amorphous fluoropolymer CytopTM is a coating material for organic nonlinear optical crystals. As a coating material, it acts as both an antireflection coating and a protective layer for the crystal itself in advanced terahertz (THz) wave generation applications. In this study, we report on the optical parameter in THz frequency over a wide temperature ranges, and the optimization of THz wave generation from a Cytop-coated nonlinear optical crystal.

We-Po3-62
Mid-IR S-SNOM Imaging Of Photo-induced Refractive Index Variation In Chalcogenide Glass
Louis Thomas¹; Sophie Eliet¹; Julie Carcreff²; Jean-François Lampin¹; Eugène Bychkov³; David Le Coq²; Pascal Masselin^3
1IEMN, France; ²Institut des Sciences Chimiques de Rennes, France; ³Laboratoire de Physico-Chimie de l'Atmosphère, France

We report the mid-IR s-SNOM surface characterization of a chalcogenide glass photo-inscribed by ultrashort laser pulses. Imaging allows to access to the morphology and the optical properties of the material at nanoscale, unravelling topographical and optical contrasts resulting from the laser inscription process.

We-Po3-63
Observation Of Strong Yellow Emission For High-conductivity ZnO Excited By Sub-terahertz Gyrotron Beam
Makoto Nakajima¹; Kosaku Kato¹; Hongsong Qiu¹; Toshihiko Shimizu¹; Nobuhiko Sarukura¹; Masashi Yoshimura¹; Tsuguo Fukuda²; Eduard Khutoryan³; Yoshinori Tatematsu³; Masahiko Tani³; Toshitaka Idehara^3
1Osaka University, Japan; ²Fukuda Crystal Laboratory Co., Ltd, Japan; ³University of Fukui, Japan

We observed yellow light emission from ZnO single crystals with high conductivity by the irradiation of sub-terahertz waves from gyrotrons. The emitted spectrum has a broad peak around 2 eV. As the spatial distribution of yellow light reflects the gyrotron beam profile and is visible with bare eyes, the high-conductive ZnO single crystals may be applied as an imager of gyrotron beam patterns usable for quick beam diagnosis.

We-Po3-64
Terahertz Spectroscopy Of Engineered Stone
Miguel Ángel Báez; Borja Vidal
Universidad Politécnica de Valencia, Spain

In this work several brands of engineered stone composites have been studied in the terahertz band. The dielectric properties of the samples were determined using THz Time Domain Spectroscopy. Imaging of the internal stone patterns was performed as well. Results show different absorptions and refractive indexes for each brand which can be related to the different compounding processes employed. This study realizes the capability of terahertz radiation as a viable way of inspection of stone composites.

We-Po3-65
Dependence Of Terahertz Conductivity Of CNT-based Macroscale Films On The CNT Length And On Plasma Exposure Time
Sergey Zhukov¹; Daria S. Kopylova²; Alexei Tsapenko²; Anna Mogogrychnaia¹; Elena Zhukova¹; Albert Nasibulin²; Boris Gorshunov^1
1Moscow Institute of Physics and Technology, Russian Federation; ²Skolkovo Institute of Science and Technology, Russian Federation

Time-domain terahertz and infrared Fourier-transform spectroscopy techniques are used to study the conductivity mechanisms of free-standing macroscale thin films composed of disordered single-walled carbon nanotubes of two types -- of various tube's lengths and films treated with oxygen plasma. We observe and analyze change in the temperature dependence of the terahertz conductance from metal-type in films with long CNTs to semiconductor-type in films with short CNTs and similar behavior of the conductance of the films with increase in the plasma exposure time.

We-Po3-66
Study On Thermionic Emission Of A W-Y Alloy Cathode Applied In Magnetron
Shikai Qi¹; Mingwei Hu²; Yang Gao¹; Li Liu¹; Wei Zeng^1
1Institute of Electronics Engineering, Jiujiang University, China; ²School of Physics and Optoelectronics Engineering, Xidian University, China

A W-Y alloy cathode applied in magnetron tube has been developed. The thermionic emission experimental results show that the dc thermionic characteristic curve of the cathode has been straight up at 1500?br with no space charge deviation point. The lifetime experimental results show that the thermionic emission current density of the cathode decreases linearly from the initial 1.5A/cm2 to 0.2A/cm2 after 80h lifetime testing at 1600?br.

We-Po3-67
Unusual Ultrafast Photocarrier Dynamics In Type II Dirac Semimetal PtTe2 Thin Film In Terahertz Band
Guohong Ma; Peng Suo
Shanghai University, China

A type II Dirac semimetal PtTe2 thin film on YAG substrate was studied at room temperature by optial pump THz probe spectroscopy. After photoexcitation, an abrupt photoinduced positive THz photoconductivity (ÃZ"ÏÆ') occurs, which was developed into negative one within time scale of a few ps, and the negative ÃZ"ÏÆ' reaches the maximum at delay time of 10 ps. The subsequent relaxation of the negative ÃZ"ÏÆ' takes place within time scale of ~700 ps. The unusual photoexcitated relaxation reflects the dynamics of holes in Dirac cone and electrons beyond the linear cone in PtTe2 thin film after photoexcitation

We-Po3-68
Active Optically Controlled Broadband Terahertz Modulator Based On Fe3O4 Nanoparticles
Luyao Xiong¹; Bo Zhang¹; Hongyu Ji¹; Wei Wang¹; Xin Liu²; Jingling Shen^1
1Capital Normal University, China ; ²Beijing Jiaotong University, China

In summary, we investigated an active optically-controlled broadband THz modulator based on Fe3O4 nanoparticles. The transmission of THz signals was modulated efficiently with an external CW laser to excite in the THz-TDS system. The modulation depth reached 92% under an external laser irradiance of 3.6 W/cm2 over a broad band (0.2--2.6 THz). The inner mechanism of this THz modulator was explained in detail by the high interface carrier densities of the hybrid structure. In addition, the limit modulated frequency of our device is ~12kHz. Thus, the results indicate that an active optically-controlled broadband THz modulator based on Fe3O4 nanoparticles was realized. The effective modulation and the ease of fabrication of our device demonstrate its wide application possibilities and its promising future in THz imaging and communication technologies.

We-Po3-69
Rotational Cuvette Measurements For Refractive Index Testing Using A THz Vector Network Analyser
Rhiannon Lees; Andreas Klein; Michael Cooke; Claudio Balocco; Andrew Gallant
Durham University, United Kingdom

This paper describes a new method for measuring the refractive index of liquids using a THz vector network analyser. The method relies on the change of optical path length in a rotating cuvette containing the liquid under test. The measured phase as a function of the cuvette angular displacement is used to calculate the refractive index of hexane, undecane and hexadecane, in the frequency range 0.8-1.05 THz.

We-Po3-70
Flexible THz Metamaterials Bonded To Paper For Chemical Sensing
Rhiannon Lees; Michael Cooke; Claudio Balocco; Andrew Gallant
Durham University, United Kingdom

We report on THz metamaterials for chemical sensing fabricated on low-loss, plastic, flexible substrates. The metamaterial is bonded to a paper sheet, which is wicked in the liquid to be analysed. Liquids with different dielectric constant result in a shift of the metamaterial resonant frequency, which can be detected by measuring its complex transmission using a THz vector network analyser, in the frequency range 0.75-1.1 THz.

We-Po3-71
Polarization Controlled Dual Resonant Tera-Hertz Transmission Through Asymmetric Aperture Array
Arnab Pattanayak¹; Goutam Rana²; Ravi Kumar Jain¹; Dipa Ghindani¹; Arkabrata Bhattacharya¹; Siddhartha P. Duttagupta²; Prasanna S. Gandhi³; Venu Gopal Achanta¹; S S Prabhu^1
1TIFR, C-225, FOTON LAB, India; ²IITB, EE Department, IIT Bombay, India; ³IITB, ME Department, Suman Mashruwala Lab, India

Resonant transmission of electromagnetic radiation through an array of rectangular apertures depends on two excited half-wavelength localized modes along the length and width of the aperture, respectively. However, due to dimension mismatch between length and width, the two excited modes do not spectrally coincide. In this paper, we conduct a study on periodic array of asymmetric aperture and demonstrate that introducing a taper along the long axis can yield both the modes simultaneously. Specifically, we show that, spectral peak positions and line-widths of these two modes can be tuned by just flipping the polarization from one state to its orthogonal state. Moreover, highly directive transmitted beam results at far field as the inter-element spacing of the aperture is reduced to half of the wavelength at resonance.

We-Po3-72
Optically Tunable Terahertz Notch Filter Based On Carbon Nanotubes
Daniel Gomon; Petr Demchenko; Victoria Soboleva; Egor Litvinov; Elizaveta Sheklanova; Mikhail Khodzitsky
ITMO University, Russian Federation

The tuning possibility of transmittance spectrum of CNT-based notch filter with cross-shaped geometry during optical pumping was shown.

We-Po3-73
Terahertz 1-bit Digital Dynamic Phase Programmable Metasurface Based On AlGaN/GaN Heterostructure
Hongxin Zeng¹; Feng Lan¹; ZiQiang Yang¹; Yaxin Zhang¹; Zongjun Shi¹; Jing Yin¹; Tianyang Song¹; Pinaki Mazumder^2
1Terahertz Research Centre, School of Electronic Science and Engineering, China; ²Department of Electrical Engineering and Computer Science, University of Michigan, United States

A terahertz 1-bit digital dynamic phase programmable metasurface (TDPM) consisting of a series of split-ring resonator (SRR) composite metamaterial with AlGaN/GaN hetero-structure as the element has been proposed to achieve dynamic beam steering and shaping. We experimentally validate the dynamic beam deflection of programmable metasurface under the different programming sequences. The terahertz beam deflects from -45Ã,° to -35Ã,° and 35Ã,° to 45Ã,° with the programming sequence 000111 and -33Ã,° to -26Ã,° and 26Ã,° to 33Ã,° with 00001111. The maximum deviation of the deflection angle is 2Ã,°. The experimental and experimental results are generally consistent with the theoretical results.

We-Po3-74
Photocontrol Phase Shifting With Extraordinary Optical Transmission Of Terahertz Waves Via Vanadium Dioxide Based Metasurface
Huajie Liang; Yaxin Zhang; Ziqiang Yang
University of Electronic Science and Technology of China, China

Here, we proposed a metasurface composed of metallic "I" structure in a hole and Vanadium Dioxide patches, which can achieve a photo induced phase shifting in Terahertz range. By combining the concepts of extraordinary optical transmission of subwavelength hole array with the dipolar resonant characteristics of the meta unit, this structure can achieve transmission resonant peak. Applying the phase transition of VO2, a continuous phase shift from 0ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,° to 76ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,° near 0.69 THz with loss of about 3dB can be obtained within single layer structure in transmission mode.

We-Po3-75
Novel Hollow Core Antiresonant Terahertz Fiber With Metamaterial Cladding
Jakeya Sultana¹; MD Saiful Islam¹; Selim Habib²; Cristiano. M. B Cordeiro¹; Alex Dinovitser¹; Brian W.-H Ng¹; Mayank Kowshik¹; Heike Ebendorff-Heidepriem¹; Derek Abbott^1
1The University of Adelaide, Australia; ²The University of Central Florida, United States

We propose a novel low loss antiresonant (AR) terahertz fiber by means of a hollow core with metamaterial cladding. The propagation of fundamental and higher order modes are investigated using Finite Element Method (FEM) based software COMSOL, and the results are compared with standard AR fiber designs. Simulation results show that the novel metamaterial structure exhibits a transmission loss reduction of an order of magnitude compared to standard AR fibers, covering a single mode bandwidth (BW) of 700 GHz.

We-Po3-76
Terahertz Broadband Linear-to-circular Polarization Deflection Based On A Birefringent Reflective Metasurface
Jing Yin¹; Feng Lan¹; Ziqiang Yang¹; Pinaki Mazumder²; Binglian Xiao¹; Hongxin Zeng¹; Luyang Wang¹; Abdur Rauf Khan^1
1School of Electronic Science and Engineering, University of Electronic Science and Technology of China, China; ²Department of Electrical Engineering and Computer Science, University of Michigan, United States

A terahertz broadband linear-to-circular (LTC) polarization deflection is proposed in this paper. By introducing a hybrid resonant structure with birefringent and broadband phase response, the polarizer can convert a linearly polarized (LP) wave to a circularly polarized (CP) wave with a deflection angle of 30Ã,°. In the 8.45% 3-dB axis ration (AR) bandwidth, the simulation results indicate that the average polarization conversion efficiency of the units reaches approximately 80% and the reflectance is 0.63 at 0.36 THz. The proposed polarization deflection has great potential application value in radar and wireless communication.

We-Po3-77
Slit Arrays For Plasmon-enhanced Vibrational Circular Dichroism: Characterization Of The Local Field Enhancement
Leonetta Baldassarre¹; Francesco Mattioli²; Giuseppe Mazzeo³; Giovanna Longhi³; Sergio Abbate³; Giovanni Pellegrini⁴; Francesco Rusconi⁴; Michele Celebrano⁴; Marco Finazzi⁴; Lamberto Duò⁴; Chiara Zanchi⁵; Matteo Tommasini⁵; Marialilia Pea⁶; Sara Cibella⁶; Filippo Sciortino¹; Alessandro Nucara¹; Michele Ortolani¹; Paolo Biagioni^7
1Department of Physics, Sapienza University of Rome, Italy; ²Istituto Fotonica e Nanotecnologie CNR, Italy; ³Università degli studi di Brescia, Italy; ⁴Dipartimento di Fisica, Politecnico di Milano, Italy; ⁵Dip. di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, Italy; ⁶Istituto di Fotonica e Nanotecnologie (IFN) CNR, Italy; ⁷Department of Physics, Politecnico di Milano, Italy

We present mid-infrared arrays of resonant chiral plasmonic nanostructures (chiral slit pairs) that are designed to feature a strong circular dichroism and an enhanced near-field optical chirality. We fabricated both right- and left-handed arrays and characterized them by means of both reflection and transmission infrared spectroscopy. Moreover, as a preliminary step towards surface-enhanced vibrational circular dichroism experiments, we experimentally studied the local field enhancement within the individual slits.

We-Po3-78
A High-precision THz Beam Steering Array Applied 2-bit Non-uniform Coding Strategy By Fractionally Dividing The Phase Gradient Distribution
Luyang Wang¹; Feng Lan¹; Pinaki Mazumder²; Hongxin Zeng¹; Ziqiang Yang¹; Jing Yin¹; Binglian Xiao¹; Ziqi Zhang¹; Zongjun Shi^1
1School of Electronic Science and Engineering, University of Electronic Science and Technology of China, China; ²Department of Electrical Engineering and Computer Science, University of Michigan, United States

A novel 2-bit coding metasurface for terahertz beam steering is proposed here. By fractionally dividing the phase gradient distribution, a higher-precision beam steering has been implemented. Compared with uniform coding manner, the novel non-uniform coding strategy employed on the proposed metasurface can shorten prominently the step length of beam steering, highly being valued for high resolution imaging and detecting.

We-Po3-79
Frequency Selective Rasorber With Continuous Tunable Transmission Band Based On Varactor
Min Guo; Qiang Chen; Yuejun Zheng; Zhanshan Sun; Yunqi Fu
College of Electronic Science, College of Electronic Science, China

This paper proposed an active FSR which is based on varactor. Simulation results shows that the center of transmission window can be tuned from 9.87GHz to 11.22GHz, with loss less than 0.75dB, and there are steady wide band with reflection coefficient below -10dB extends from 5.65GHz to 15.39GHz. Since the total equivalent capacitance Ce of the resistive element is got by serial capacitance of double helix C and varactor Ct, and C is less than Ct in most cases. Thus, the total equivalent C cannot be changed in wide range. Thus, the transmission frequency cannot be changed in wideband. Therefore, the transmission window can be tuned in wideband is needed to studied in future research.

We-Po3-80
High-Performance And Low-Crosstalk Terahertz Plasmonic Crossings
Mingrui Yuan¹; Ying Zhang¹; Yongchang Lu¹; Yanfeng Li¹; Jianqiang Gu¹; Jiaguang Han¹; Weili Zhang^2
1Tianjin University, College of Precision Instrument and Optoelectronic, Center for Terahertz Waves, China; ²Oklahoma State University, School of Electrical and Computer Engineering, United States

For terahertz integrated systems, an intersection between waveguides is inevitable and is often accompanied by considerable crosstalk and loss. Here, we propose and experimentally demonstrate a novel type of crossing with a footprint less than 0.2 mm×0.2 mm for terahertz surface plasmon polariton waveguiding. The crossing loss is estimated by investigating a sequence of waveguides with one, two and three crossings. By optimizing the crossover structure to suppress crosstalk, the measured loss is as low as -3.4 dB and the crosstalk is less than -19.12 dB/crossing at 0.55 THz. Furthermore, the relationship between crosstalk and crossing angle is discussed.

We-Po3-81
Radiation From Junctions Between Two-dimensional Plasmonic Waveguides
Oleksiy Sydoruk; Serhii Siaber; Simone Zonetti
Imperial College London, United Kingdom

There has been recent interest in the retardation regime of plasmon propagation in two-dimensional electron systems, when the plasmon and the light velocities are comparable to each other. The usual electrostatic approximation is no longer valid, and a plasmon incident upon a junction can scatter into radiation modes. Here, we will present theoretical analysis of junctions between two-dimensional plasmonic waveguides in the retardation regime and discuss (i) the plasmon scattering for different relationships between the plasmon and the free-space wavenumbers, (ii) numerical and approximate analytical solutions to the problem, (iii) implications of the result for the design of plasmonic devices.

We-Po3-82
Metal-graphene Stacking Structure For Dynamical Tunable Ultra-wide Band Absorbers
Renbin Zhong; Yan Liu; Yilin Lv; Chen Han; Wang Yiqing; Shenggang Liu
University of Electronic Science and Technology of China, China

By construction metal-graphene metamaterial with simple gold strips parallel or side-by-side arranged on a monolayer graphene as molecular cells, multi-band and ultra-wide band absorber can be achieved at mid-infrared frequencies. The extremely absorption bandwidth up to 11.8THz can be obtained, the intensity exceeds 90% at the absorption peak. Independently tunable multi-band and ultra-wide band absorber is also explored by stacking molecular cells with two or three layers. The results will benefit the integrated micro-structure research with flexible tunability, and the multilayer structure has potential applications in tunable filtering, sensing, cloaking objects and other multispectral devices.

We-Po3-83
X-Shaped Metamaterial Biosensor Combined With Microfluidic System For Different IPA Concentration Measurement
Shih Ting Huang¹; Yu Ting Hu¹; Ta Jeng Yen²; Da Jeng Yao²; Steve Hsu³; Kai-Yuan Tang^3
1Department of Power Mechanical Engineering, National Tsing Hua University, Taiwan; ²National Tsing Hua University, Taiwan; ³ACE Biotek Co.,Ltd., Taiwan

X-shaped plasmonic biosensor (XPS) can have strong sensitivity within THz spectrum combined with microfluidic system. The microfluidic system can provide low volume reagents for detection, reduce noise from environment, and concentrate the sample on detection spots. TeraPulse 4000 equipment can be used for the measurement for biosensor, by observing variation of refractive index in THz frequency domain spectrum. The results show metamaterial device in comparison of different concentration of IPA, where refractive index reflects absorption of liquids. Furthermore, the effect of FOM and quality factor can be observed through resonant dip at designed 0.20898 THz.

We-Po3-84
Effects Of Substrate Phonon Absorption On The Resonance Properties Of Ultrathin Metamaterials In The Terahertz Range
Tianye Niu¹; Boqi Qiu¹; Ya Zhang²; Kazuhiko Hirakawa^1
1Institute of Industrial Sicence, University of Tokyo, Japan; ²Tokyo University of Agriculture and Technology, Japan

We have investigated the reflection spectra of metal-insulator-metal (MIM) metamaterial absorbers (MMAs) in top-incidence and bottom-incidence configurations in terahertz (THz) frequency range. Top-incidence MIM MMAs show narrowband and large absorption, but no resonant mode is observed GaAs-based bottom-incidence MIM MMAs due to strong phonon absorption in GaAs substrate. 63% absorption peak is observed in Si-based bottom-incidence MIM MMAs, which becomes a good candidate for the integration with THz MEMS bolometer.

We-Po3-85
Multipole Terahertz Localized Plasmon Resonances On Spiral Structures
Vasily Gerasimov¹; Sergey Kuznetsov²; Alexey Lemzyakov³; Ruslan Hafizov^4
1Budker Institute of nuclear physics SB RAS, Russian Federation; ²Rzhanov Institute of Semiconductor Physics SB RAS, "TDIAM", Russian Federation; ³Budker Institute of nuclear physics SB RAS, Russian Federation; ⁴Novosibirsk State University, Russian Federation

Numerical simulations of sub-wavelength single and double logarithmic spiral metal disk array in the range of 0.04 - 5 THz have shown that high order localized surface plasmon resonances arise at oblique incidence and small gap sizes between the disks. The spectra and 2D distributions of the EM field at the resonant frequencies depend on the geometry of the structure, period of the array, and a gap between the disks in the doubled spiral structures, but there is no dependence on the twisting direction of the spirals.

We-Po3-86
Investigation Of The Reflectivity Spectra Of N-type GaN Semiconductor With Surface Relief Grating
Vytautas Janonis¹; Pawel Prystawko²; Krzysztof Gibasiewic²; Jacek Kacperski²; Irmantas Kasalynas^1
1Center for Physical Sciences and Technology, Lithuania; ²Institute of High Pressure Physics Polish Academy of Sciences, Poland

Reflectivity spectra of n-type GaN with a shallow or deep relief grating were investigated theoretically and experimentally in the spectrum range of 100-1500 cm-1. The surface Phonon-Plasmon-Polariton modes for the strong field confinement within GaN micro-cavities were engineered by proper selection of the periodicity, filling factor, and depth of the groves. Application of such surface relief gratings is important for the development of total power absorbers, filters, waveguides, and other types of optoelectronic devices.

We-Po3-87
Independent Linear Dual-polarization Terahertz Focusing At A Composite Multifunctional Metasurface
Wei Kou¹; Yaxin Zhang¹; Shixiong Liang²; Zhihong Feng¹; Ziqiang Yang^1
1Terahertz Science Cooperative Innovation Center, University of electronic science and technology, China; ²National Key Laboratory of Application Specific Integrated Circuit, Hebei Semiconductor Research Ins, China

In this paper, we present a multifunctional metasurface enabling terahertz focusing for efficient terahertz wave control. Two different focal distances can be achieved under a normal incident wave with two different linear polarization. Further, the incident waves will form vertical or parallel axial focus with p(x) or s(y)-polarized component. In addition, this design method can be applied to other terahertz multifunctional devices which develops diversifications of the metasurface.

We-Po3-88
Enhanced Terahertz Smith-Purcell Radiation From Subwavelength Holes Array Within Metamaterials
Weihao Liu; Zijia Yu; Yucheng Liu; Qika Jia; Yalin Lu
University of Science and Technology of China, China

We propose to generate coherent terahertz radiation by using free-electron beams to excite arrays of rectangular sub-wavelength holes within metamaterials. The radiation is achieved due to the constructive interference of radiation from all sub-wavelength holes of the array via Smith-Purcell effect. Compared with that in conductor holes, the resonant modes in metamaterial holes have much higher intensity thanks to the excitation of terahertz surface plasmons. Thus, it can generate terahertz radiation with much higher intensity. Also, its radiating direction can be adjusted by changing the arrangement of the array. It offers a promising way of developing efficient and steerable terahertz sources.

We-Po3-89
Broadband Terahertz Modulator Based On Fin-line With Meta-atom
Xu Hou¹; Ting Zhang²; Yaxin Zhang²; Ziqiang Yang²; Shixiong Liang^3
1Terahertz Science Cooperative Innovation Center, China; ²Terahertz Science Cooperative Innovation Center, University of Electronic Science and Technology of, China; ³National Key Laboratory of Application Specific Integrated Circuit, Hebei Semiconductor Research Institute, China

In this paper, we present a broadband terahertz (THz) amplitude modulator by combining fin-line with meta-atom. The resonant mode of the meta-atom is controlled by the HEMT diode whose switch is controlled by the bias voltage. Consequently, the THz wave transmitted in the waveguide can be amplitude modulated. This terahertz modulator has a bandwidth of 60 GHz and relatively low insertion loss. This work may bring many potential applications for THz communication.

We-Po3-90
Phase Singularity In Double-layer Metamaterial Based On Lattice Resonance
Zhengli Han¹; Seigo Ohno²; Hiroaki Minamide^1
1Riken, Japan; ²Tohoku University, Japan

Electromagnetic wave experiences phase changing both in propagation and resonance. Extreme phase changing is interesting and has its applications. Here we report a phase singularity phenomenon in double-layer metamaterial.

We-Po3-91
Terahertz Chemical Sensor Based On The Plasmonic Hexagonal Microstructured Holes Array In Aluminum
ABHISHEK PANGHAL; Ravi Kumar Jain; Arnab Pattanayak; Arkabrata Bhattacharya; Venu Gopal Achanta; Shriganesh Prabhu
Tata Institute of Fundamental Research, India

Terahertz Chemical sensor based on the hexagonal microstructure air holes in a free-standing Aluminum foil having a thickness ~ 11 µm has been designed by numerical simulations which are further optimized and fabricated by Computerized Numerical Control (CNC) drilling machine. Localized plasmons (LPs) excited at the air holes are used to demonstrate refractive index sensing for liquids. The proposed sensor would be a potential device for liquid sensing applications.

We-Po3-92
Topologically Protected Tera-Hertz Loop Yagi-Uda Absorber
Arnab Pattanayak¹; Ravi Kumar Jain¹; Dipa Ghindani¹; Goutam Rana²; Sandipta Roy³; Siddhartha P. Duttagupta⁴; Prasanna S. Gandhi⁵; Venu Gopal Achanta¹; S S Prabhu^1
1TIFR, C-225, FOTON LAB, India; ²IITB, EE Department, India; ³IITB, CRNTS, India; ⁴IITB, EE Department, Electrical Engineering, India; ⁵IITB, Suman Mashruwala Lab, ME Department, India

A loop Yagi-Uda array can be used as an efficient, polarization independent and narrowband absorber in the THz regime. The elementary unit of the array consists of three-stacked gold micro-rings, which are separated from each other by thick SU-8 layer. Here, we present a topological study of a loop Yagi-Uda structure to examine the robustness of the narrow absorption peak against the misalignment among multiple layers and structural disorders. The study reveals that misalignment and variation of geometrical parameters with in the range of experimental errors can still protect the absorption peak with more than 70% absorption.

We-Po3-93
Optical Activity Of Graphene-Based Chiral Metasurface In THz Frequency Range
Maxim Masyukov; Anna Vozianova; Kseniia Gubaidullina; Alexander Grebenchukov; Mikhail Khodzitsky
ITMO University, Russian Federation

In this paper the optical activity of two types of graphene-based chiral metasurfaces was studied. The gammadion resonators of the unit cell were partly made of graphene. Three resonant frequencies of the metasurfaces in the frequency range of 0.1-0.5 THZ were found. It is shown that the value of optical activity strongly depends on the chemical potential of graphene petals, as well as on the position of graphene inclusions.

We-Po3-94
Optical Activity Of Graphene-Based Chiral Metasurface In THz Frequency Range
Maxim Masyukov; Anna Vozianova; Kseniia Gubaidullina; Alexander Grebenchukov; Mikhail Khodzitsky
ITMO University, Russian Federation

In this paper the optical activity of two types of graphene-based chiral metasurfaces was studied. The gammadion resonators of the unit cell were partly made of graphene. Three resonant frequencies of the metasurfaces in the frequency range of 0.1-0.5 THZ were found. It is shown that the value of optical activity strongly depends on the chemical potential of graphene petals, as well as on the position of graphene inclusions.

We-Po3-95
Electromagnetic Modeling Of Human Skin As A Receiving And Transmitting Antenna Array In Sub-THz
Noa Betzalel; Alexander Puzenko; Paul Ben Ishai; Yuri Feldman
The Hebrew University of Jerusalem, Israel

The helical sweat ducts (HSD) in human skin were anchored as the dominant structure of skin governing its electromagnetic (EM) behavior in the millimeter wave (MMW) range. We present an improved EM human skin model in the Y-band, which is rather complicated as it takes the fine structure of the upper skin layer, into account, together with its dielectric properties. We present for the first time, the transmitting mode of human sweat ducts, as well as its receiving mode. In addition, by considering the eccrine sweat ducts as interactive elements with non-random distribution, we demonstrate for the first time an antenna-array-like behavior of human sweat ducts.

We-Po3-96
Characterization Of Epoxy-Silver Nanoparticles Composites In Microwave And Millimeter-wave Regime
Shih-Chieh Su; Tsun-Hsu Chang
Department of Physics, National Tsing Hua University, Taiwan

We prepare artificial materials composed of silver nanoparticles and epoxy resin. Then we characterize the permittivity and permeability of the composites in the microwave and millimeter-wave regime. Measured permittivities and permeabilities exhibit interesting tendency along with the volume concentration. As the concentration of the silver nanoparticle increases, the dielectric constant will be enhanced, but the magnetic properties become diamagnetism. Both electric and magnetic properties show an abnormal effect when compares to the bulk silver.

We-Po3-97
Independently Tunable Dual-band Metamaterial Absorber Based On Graphene At Mid-infrared Frequencies
Chen Han; Renbin Zhong; Yilin Lv; Yiqing Wang; Long Yang; Anchen Ma; Shenggang Liu
Terahertz Research Center, School of Physical Electronics, University of Electronic Science and Tech, China

Despite the great achievement in understanding of the graphene-based metamaterial absorbers (GMAs), the limitations such as single narrowband absorption, low absorption peak and multiple bands that can't be independently tuned have not been completely overcome. This paper reports a dual-band absorber through etching two cascaded metallic resonators with different sizes in the unit cell of GMA. Two independently tunable absorption bands with absorption peaks greater than 99% are obtained at mid-infrared frequencies.

We-Po3-98
Bifunctional Metasurface For Polarization-controlled Beam Steering And Excitation Of Spoof Surface Plasmon Polariton
Li-Zheng Yin; Feng-Yuan Han; Tie-Jun Huang; Jiang-Yu Liu; Pu-Kun Liu
Peking University, China

Based on the combination of propagation with geometric phase, to the best of our knowledge, a new reflective metasurface which can control the direction of reflected waves and excite spoof surface plasmon polariton (SSPPs) simultaneously is proposed and numerically demonstrated. The incident waves can be converted into SSP with longitudinal wave vector kx = 1.2 k0 or anomalously reflected with reflection angle ?r = 13.9Ã,º under the illumination of the left or the right circular polarization beam, respectively. The respective converting efficiency of the left and right circular polarization can reach up to 70% and 82% at the frequency of 0.3 THz. Our study may open up new routes for polarization-related antennas, detectors, and other practical terahertz devices.

We-Po3-99
Terahertz Emission Due To Radiative Decay Of Hot 2D Plasmons In AlGaN/GaN Heterojunction
Vadim Shalygin¹; Maria Moldavskaya¹; Maxim Vinnichenko¹; Vadim Panevin¹; Kirill Maremyanin²; Dmitry Firsov¹; Leonid Vorobjev¹; Alexey Sakharov³; E Zavarin³; Dmitry Arteev³; Wsevolod Lundin³; Vadim Korotyeyev⁴; Sami Suihkonen⁵; Christoffer Kauppinen^5
1Peter the Great St. Petersburg Polytechnic University, Russian Federation; ²Institute for Physics of Microstructures of RAS, Russian Federation; ³Ioffe Institute, Russian Federation; ⁴Institute of Semiconductor Physics NASU, Ukraine; ⁵Aalto University, Finland

Emission of terahertz radiation from a AlGaN/GaN/Al2O3 heterostructure with a surface metal grating is investigated under conditions of 2D electron heating in a lateral electric field. The studies are performed under essentially non-equilibrium conditions when the effective temperatures of 2D electrons and 2D plasmons are several times higher than the lattice temperature. This makes it possible to observe and explore high-quality peaks of intense THz radiation corresponding to 2D plasmon resonance.

We-Po3-100
Research Of Volume Free-Electron Laser With Photonic Crystal Structure For Operation In Sub-Terahertz Range
Artem Badarin¹; Semen Kurkin²; Andrey Starodubov¹; Nikita Frolov²; Alexey Koronovskii^1
1Saratov State University, Russian Federation; ²Innopolis University, Russian Federation

In this work, we present the results of the numerical optimization of volume free-electron laser based on the interaction between an electron beam and periodic structure of microwave photonic crystal. The optimization aims at the advancement of such device to the sub-terahertz frequency range. We show that the reduction of characteristic geometric dimensions allows increasing the working frequency of photonic crystal fundamental mode up to 12.5 GHz. Moreover, we observe the possibility to generate microwaves at the fifth harmonic of the fundamental frequency, namely f=62.5 GHz and obtain an output power level of about 3.6 kW.

We-Po3-101
Design Of The Planar MIG For 28 GHz Gyrotron With The Rectangular cavity
Mariusz Hruszowiec; Tadeusz Więckowski; Edward F. Pliński
Wroclaw University of Science and Technology, Poland

For a planar gyrotron with a rectangular cavity the classical cylindrical MIG is not adequate for the best solution for generating the electron beam with an appropriate parameters. Since the required shape of the electron beam needs to be in pencil like, the emitter shape needs to be rectangular. The approach to design that kind of the MIG with rectangular emitter is considered

We-Po3-102
The Interaction Between Two-dimensional Electron Gas And Terahertz Plasma Wave In HEMT-like Structure
Yilin Pan; Ping Zhang; Yaming Chen; Hexin Wang; Kaicheng Wang; Zhanliang Wang; Zhigang Lu; Huarong Gong; Zhaoyun Duan; Yubin Gong
University of Electronic Science and Technology of China, China

An interaction between two-dimensional electron gas and terahertz plasma wave in HEMT-like structure is rigorously analyzed, the dispersion relation is derived and the effect of frequency on gain is investigated. The results show that the terahertz device has considerable performance and the gain of the terahertz wave decreases with the frequency increasing at terahertz wave band, which can provide theoretical prediction for the terahertz amplifier based on the HEMT-like structure.

We-Po3-103
Design And Implementation Of A Terahertz Integrated Lens-Antenna For A Nanocontacts Based Photomixer
Verónica Laín Rubio; Shihab Al-Daffaie; Alaa Jumaah; Thomas Kusserow
Technische Universität Darmstadt, Germany

A new integrated lens-antenna is designed and implemented for a nanocontact based terahertz (THz) photomixer. The new design replaces the standard conventional bulky silicon lens, which normally no THz device can avoid. The Fresnel Zone Plate (FZP) is used to design the new lens-antenna and is simulated on the MIT open-source tool called Meep. The final design showed, with only two simple fabrication technology processing steps (normal optical lithography) that the lensantenna can be implemented including the THz photomixer. The simulation and the fabrication results showed promising results towards the THz measurements, compared with the conventional bulky silicon lens.

We-Po3-104
Microstrip Waveguide Loaded With Metamaterial Structure For Sensitive Resonant Detection
Josip Vukusic; Philippe Tassin
Chalmers University of Technology, Sweden

We present results on coupled microstrip resonators at W-band, albeit scalable up in frequency, that can be utilized as highly sensitive detectors. By incorporating tunable varactor circuits, we will explore the possibility of resolving spectral features, i.e qualitative analysis of a materials frequency response

We-Po3-105
Strong Anisotropic Photo-mixing Effect In Semi-Dirac Materials In The Terahertz Regime
Sunchao Huang; Jack Zuber; Enbang Li; Chao Zhang
School of Physics, University of Wollongong, Australia

The results show a strong anisotropic photo-mixing response in the x and the y directions. The anisotropic effect mainly arises from the unique energy-momentum dispersion.

We-Po3-106
Bandgap Dependence Of Hot Electron Relaxation In Three Dimensional Dirac Semi-Metals
Sunchao Huang; Jack Zuber; Enbang Li; Chao Zhang
School of Physics, University of Wollongong, Australia

The results show a finite bandgap in Cd3As2 releases the selection rule in the hot carrier relaxation process, which leads to a faster cooling. Additionally, the total power loss has a parabolic dependence on bandgap.

We-Po3-107
Fabrication Of Broadband Absorbers For The Far-Infrared Spectral Range
Aditi Upadhyay¹; Xiaolong You²; Christophe Fumeaux²; Madhu Bhaskaran¹; Sharath Sriram¹; Withawat Withayachumnankul^2
1RMIT University, Melbourne, Australia; ²The University of Adelaide, Australia

A broadband electromagnetic wave absorber is presented. The absorption band spans nearly the entire far-infrared regime. This absorber is non-resonant and utilizes silicon micromachining techniques. The structure is made of a doped silicon wafer whose surface is etched anisotropically to form a two-dimensional array of inverse pyramid cavities. Far-infrared waves incident onto this structure undergo multiple reflections by the slant walls and the energy of the incident waves is partially absorbed by the wall at each reflection, and eventually fully dissipated therein. The absorbance of the structure is at least 90% across the far-infrared band from 1.25 THz-5.00 THz, and can be further extended with a thicker substrate.

We-Po3-108
Hot Electron Y-Ba-Cu-O Bolometer Heterodyne Mixers: Stand-off Target Passive Detection Performance Modeling
Romain Ladret¹; Vishal Jagtap¹; Annick Degardin²; Alain Kreisler^1
1CentraleSupelec/GeePs, France; ²Sorbonne-University/GeePs, France

The development of Y-Ba-Cu-O hot electron bolometers (HEBs) has been delayed for several decades, mainly due to premature aging of the ultrathin Y-Ba-Cu-O films hampering the HEB function. The improvement efforts were comforted by early performance predictions using the point bolometer approach, further confirmed by the 1-D hot spot model. This latter model was then extended to include the Y-Ba-Cu-O constriction behavior at THz frequencies. The HEB performance has been simulated in terms of noise temperature TN and conversion gain G, for a device constriction of length = width = 400 nm and thickness = 35 nm, obtaining, e.g. TN = 1030 K (double sideband) and G = -6.1 dB at 2.5 THz (12.5 Ã,µW local oscillator power). A stand-off passive detection scheme performance is also discussed in terms of achievable target differential temperature resolution, spatial resolution and atmospheric absorption as a function of the HEB mixer instantaneous bandwidth.

We-Po3-109
Design Of Diode Type Magnetron Injection Gun For 170GHz Gyrotron
Alok Mishra¹; Anirban Bera²; M. V. Kartikeyan^3
1CSIR-CEERI, MWD DIVISION, India; ²CSIR-CEERI, PILANI, India; ³IIT-ROORKEE, India

This paper presents the electron gun design study of using diode-type magnetron injection guns (MIGs) for 1MW, 170GHz gyrotron operated on the TE28,12 mode. The initial design has done through the computational analysis and the design optimization achieved with the help of EGUN beam trajectory program. Further, the feasibility of the designed gun type also has been discussed.