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[IEEE NAECON 2019 - IEEE National Aerospace and Electronics Conference - Dayton, OH, USA (2019.7.15-2019.7.19)] 2019 IEEE National Aerospace and Electronics Conference (NAECON) - Development of Optically Controlled Tunable/Reconfigurable Terahertz Waveguide Circuits/Components For Advanced Sensing and Adaptive Wireless Communications
摘要： We report our recent progress toward the development of optically controlled tunable/reconfigurable THz circuits/components in waveguide configurations for advanced sensing and adaptive wireless communications. The development and demonstration of a modified WR-4.3 variable waveguide attenuator based on photo-excited Si with 60-dB range and 0.7-dB insertion loss will first be reviewed. Then the investigation of a WR-5.1 reconfigurable band-stop filter (BSF) prototype based on photo-induced electromagnetic band gap (PI-EBG) structures using semiconductor mesa arrays will be presented. The center frequency of the BSF can be reconfigured from 166-200 GHz with adjustable stop-band rejection and bandwidth. Finally, the development of high-performance THz integrated switches using the same optical control methodology will be envisioned, investigated and discussed. Preliminary results reveal that the optically controlled RF figure-of-merit (evaluated by RonCorr constant) of 153 THz, allowing them to outperform both conventional solid-state-device-based (e.g., HEMTs) and emerging phase-changing-material-based (e.g., VO2) counterparts, and therefore promising to compete with MEMS switches in the mmW-THz region for a novel class of tunable/reconfigurable circuits/components.
关键词： Terahertz,tunable/reconfigurable,imaging,waveguides,optical tuning,wireless communication,THz devices
更新于2025-09-23 15:19:57
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Four-channel THz wave routing switch based on magneto photonic crystals
摘要： A four-channel routing switch based on a square lattice 2-D silicon photonic crystal with four point defects and five line defects is proposed. In this scheme, the properties that magnetic permeability of the ferrite material changing with external magnetic field and the coupling characteristics between line defect and point defect are used. The proposed device is theoretically analyzed and numerically investigated by using plane wave method (PWM) and finite-difference time-domain (FDTD). The results show that the four-channel routing switch can be realized by applying different intensity of magnetic fields. The extinction ratios of the four channels are all more than 13dB, the transmittance rates are higher than 93%, the insertion losses are lower than 0.288dB, and steady times are less than 50 ps. The proposed THz routing switch has potential applications in terahertz wave integrated circuit fields in the future.
关键词： THz wave；routing switch；magneto photonic crystal
更新于2025-09-23 15:19:57
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Terahertz and Visible Probing of Particles Suspended in Air
摘要： The attenuation of air suspended particles is measured with a terahertz time-domain spectrometer (THz-TDS). Simultaneously, the attenuation at a wavelength of 650 nm is probed with a laser diode. On the one hand, this dual measurement allows a direct assessment of the visibility evolution in the THz range compared to the visible range. On the other hand, this setup provides an estimation of the scattering strength and the density of particles. Using the Mie theory, the method is successfully applied to experimentally characterize the refractive index of sand grains and glass beads. The refractive indices of sand grains and glass beads, average over the acquisitions, are 1.67 and 2.54, respectively. The estimation of the scattering properties of sand grains are crucial to evaluate the performance of THz systems to image through brownout clouds that are created by helicopter rotors when landing in arid areas.
关键词： THz scattering,propagation,refractive index,THz time-domain spectroscopy
更新于2025-09-19 17:15:36
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Metalized Poly-methacrylate Off-Axis Parabolic Mirrors for Terahertz Imaging Fabricated by Additive Manufacturing
摘要： Terahertz radiation sources are currently one of the most widely used non-ionizing illumination mechanisms for security applications and also find increasing utilization in quality control of commercial products. Presently, a majority of these applications rely on scanning rather than direct imaging and implicitly suffer from temporal latency due to post processing. The monetary and temporal cost associated with procuring commercially manufactured optics that are suitable for imaging leads to fundamental limitations in the ability to rapidly develop application-specific imaging modalities using terahertz sources. Herein, we show a novel method for the rapid prototyping of metallic coated poly-methacrylate parabolic reflectors fabricated by stereolithographic 3D printing. Images comparing the performance of a commercially available off-axis parabolic reflector to our metalized poly-methacrylate prototype, which was designed to be identical to the commercially available mirror, are subsequently presented. The images show that at 530 GHz it is possible to produce a metalized poly-methacrylate off-axis paraboloid whose spatial beam profile is nearly identical to that of a commercially available equivalent.
关键词： Rapid prototyping,3D printing,THz imaging
更新于2025-09-19 17:15:36
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[IEEE 2018 11th Global Symposium on Millimeter Waves (GSMM) - Boulder, CO, USA (2018.5.22-2018.5.24)] 2018 11th Global Symposium on Millimeter Waves (GSMM) - High-Resolution Antenna Near-Field Imaging and Sub-THz Measurements with a Small Atomic Vapor-Cell Sensing Element
摘要： Atomic sensing and measurement of millimeter-wave (mmW) and THz electric fields using quantum-optical EIT spectroscopy of Rydberg states in atomic vapors has garnered significant interest in recent years towards the development of atomic electric-field standards and sensor technologies. Here we describe recent work employing small atomic vapor cell sensing elements for near-field imaging of the radiation pattern of a Ku-band horn antenna at 13.49 GHz. We image fields at a spatial resolution of λ/10 and measure over a 72 to 240 V/m field range using off-resonance AC-Stark shifts of a Rydberg resonance. The same atomic sensing element is used to measure sub-THz electric fields at 255 GHz, an increase in mmW-frequency by more than one order of magnitude. The sub-THz field is measured over a continuous ±100 MHz frequency band using a near-resonant mmW atomic transition.
关键词： atom,microwave,electric field,metrology,quantum sensing,millimeter-wave,THz,antenna,mmW,Rydberg,terahertz,Atomic sensors,antenna characterization
更新于2025-09-19 17:15:36
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Conformational assignment of gas phase peptides and their H-Bonded complexes using far-IR/THz: IR- UV ion dip experiment, DFT-MD spectroscopy, and Graph Theory for modes assignment.
摘要： The combined approach of gas phase IR-UV ion dip spectroscopy experiments and DFT-based molecular dynamics simulations for theoretical spectroscopy reveals the 3D structures of (Ac-Phe-OMe)1,2 peptides using the far-IR/THz signatures. Both experimental and simulated IR spectra are well-resolved in the 100-800 cm?1 domain, allowing an unambiguous assignment of the conformers, that could not be achieved in other more congested spectral domains. We also present and make proofs-of-principles for our newly developed theoretical method for the assignment of (anharmonic) vibrational modes from MD simulations based on Graph Theory coupled to APT weighted-internal coordinates velocities DOS spectra. The principles of the method are reviewed, applications to the simple gas phase water and NMA (N-Methyl-Acetamide) molecules are presented, and the application to the more complex (Ac-Phe-OMe)1,2 peptidic systems shows that the complexity in assigning vibrational modes from MD simulations is released with the graphs. Our newly developed graph-based methodology is furthermore shown to allow an easy comparison between the vibrational modes of isolated monomer(s) and their complexes, as illustrated by the (Ac-Phe-OMe)1,2 peptides.
关键词： gas phase peptides,vibrational modes assignment,far-IR/THz spectroscopy,Graph Theory,IR-UV ion dip,DFT-MD simulations,β-sheet structures
更新于2025-09-19 17:15:36
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Thermostimulated THz Radiation Emission of GaAs at Surface Plasmon-Phonon Polariton Frequencies
摘要： The THz radiation reflection, absorption and emission spectra of conductive n-GaAs/air surface are considered. The influence of thermostimulated surface plasmon-phonon (SPP) polariton oscillations on THz radiation reflection, absorption and emission of high conductivity GaAs polished plates with electron density n = 7·1017 cm–3 and 4·1018 cm–3 and thickness of 350 μm is studied experimentally. The frequencies of thermostimulated transverse and longitudinal optical phonons and SPP oscillations, which characterize a heated lattice state, were determined. It is found that the heated highly doped interface layer (GaAs/air) emits the THz radiation at selected frequencies of SPP oscillations in the (7 – 8) THz and (10 – 15) THz ranges. It is shown that thermal heating of the GaAs/air interface enhances the absorption of the incident THz radiation. The huge decrease of the incident radiation reflectivity at the SPP frequencies with an increase of GaAs temperature is observed experimentally.
关键词： surface plasmon-phonon polaritons,black-body radiation,GaAs,thermostimulated THz radiation emission
更新于2025-09-19 17:15:36
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Terahertz surface and interface emission spectroscopy for advanced materials
摘要： Surfaces and interfaces are of particular importance for optoelectronic and photonic materials as they are involved in many physical and chemical processes such as carrier dynamics, charge transfer, chemical bonding, transformation reactions and so on. Terahertz (THz) emission spectroscopy provides a sensitive and nondestructive method for surface or interface analysis of advanced materials ranging from graphene to transition metal dichalcogenides, topological insulators, hybrid perovskites, and mixed-dimensional heterostructures based on two-dimensional materials. In this review paper, we start with the THz radiation mechanisms under ultrafast laser excitation. Then we concentrate on the recent progresses of THz emission spectroscopy on the surface and interface properties of advanced materials, including transient surface photocurrents, surface nonlinear polarization, surface states, interface potential, and gas molecule adsorption/desorption processes. This novel spectroscopic method can not only promote the development of new and compact THz sources, but also provide a nondestructive optical method for surface and interface characterization of photocurrent and nonlinear polarization dynamics of materials.
关键词： THz emission spectroscopy,transient photocurrent,advanced material,surface and interface,nonlinear polarization
更新于2025-09-19 17:15:36
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Up to 70 THz bandwidth from an implanted Ge photoconductive antenna excited by a femtosecond Er:fibre laser
摘要： Phase-stable electromagnetic pulses in the THz frequency range offer several unique capabilities in time-resolved spectroscopy. However, the diversity of their application is limited by the covered spectral bandwidth. In particular, the upper frequency limit of photoconductive emitters - the most widespread technique in THz spectroscopy – reaches only up to 7 THz in the regular transmission mode due to absorption by infrared-active optical phonons. Here, we present ultrabroadband (extending up to 70 THz) THz emission from an Au-implanted Ge emitter that is compatible with mode-locked ?bre lasers operating at wavelengths of 1.1 and 1.55 μm with pulse repetition rates of 10 and 20 MHz, respectively. This result opens up the possibility for the development of compact THz photonic devices operating up to multi-THz frequencies that are compatible with Si CMOS technology.
关键词： photoconductive antenna,Si CMOS technology,THz emission,Ge emitter,femtosecond fiber lasers
更新于2025-09-19 17:13:59
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Ultrahigh Q-factor dual-band terahertz perfect absorber with dielectric grating slit waveguide for sensing
摘要： Terahertz (THz) perfect absorber with ultra-narrow bandwidth at near-unity absorbance has been a challenging issue due to mutual restriction of elemental requirements in design. Here, we propose an extremely sharp dual-band THz perfect absorber with ultrahigh Q-factor and near-unity absorbance by incorporating a Fabry-Perot micro-cavity into dielectric grating slit waveguide. Full-wave simulation demonstrates that the proposed structure not only achieves ultra-narrow band perfect absorption with an ultrahigh Q-factor of 4600 in THz regime, but also shows extraordinary sensing performance with a record figure of merit (FOM) of 2415 at THz frequencies. The optimized guided mode resonance leads to the ultrahigh Q-factor through suppressing the absorption and radiation losses. The enhanced interaction between the cavity localized fields and the analytes significantly improves THz sensing capability. Our design approach shows a promising future in simple and inexpensive THz biochemical sensors.
关键词： THz sensing,Terahertz wave,perfect absorber,ultrahigh Q-factor
更新于2025-09-19 17:13:59