- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Understanding the Sidewall Dependence of Loss for Ge-on-Si Waveguides in the Mid-Infrared
摘要： An empirical model for field-effect transistor (FET) based power detectors is presented. The electrical model constitutes a Volterra analysis based on a Taylor series expansion of the drain current together with a linear embedding small-signal circuit. It is fully extracted from S-parameters and IV curves. The final result are closed-form expressions for the frequency dependence of the noise equivalent power (NEP) in terms of the FET intrinsic capacitances and parasitic resistances. Excellent model agreement to measured NEP of coplanar access graphene FETs with varying channel dimensions up to 67 GHz is obtained. The influence of gate length on responsivity and NEP is theoretically and experimentally studied.
关键词： field-effect transistors (FETs),Volterra,terahertz detectors,microwave detectors,graphene,power detectors,Analytical model
更新于2025-09-23 15:21:01
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Refractive Index Sensing Research on Multi-Fano-Based Plasmonic MDM Resonant System With Water-Based Dielectric
摘要： In this letter, we report initial experimental results which provide the foundation for low-terahertz (low-THz) radar imagery for outdoor unstructured scenarios as expected in automotive sensing. The requirements and speci?cations for a low-THz single imaging radar sensor are brie?y outlined. The imaging capabilities of frequency-modulated continuous-wave (FMCW) radar operating at 150 GHz are discussed. A comparison of experimental images of on-road and off- road scenarios made by a 150-GHz FMCW radar and a reference 30-GHz stepped-frequency radar is implemented, and their performance is analyzed.
关键词： low terahertz (low-THz),Imaging radar
更新于2025-09-23 15:21:01
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Quantum cascade laser based hybrid dual comb spectrometer
摘要： Four-wave-mixing-based quantum cascade laser frequency combs (QCL-FC) are a powerful photonic tool, driving a recent revolution in major molecular fingerprint regions, i.e. mid- and far-infrared domains. Their compact and frequency-agile design, together with their high optical power and spectral purity, promise to deliver an all-in-one source for the most challenging spectroscopic applications. Here, we demonstrate a metrological-grade hybrid dual comb spectrometer, combining the advantages of a THz QCL-FC with the accuracy and absolute frequency referencing provided by a free-standing, optically-rectified THz frequency comb. A proof-of-principle application to methanol molecular transitions is presented. The multi-heterodyne molecular spectra retrieved provide state-of-the-art results in line-center determination, achieving the same precision as currently available molecular databases. The devised setup provides a solid platform for a new generation of THz spectrometers, paving the way to more refined and sophisticated systems exploiting full phase control of QCL-FCs, or Doppler-free spectroscopic schemes.
关键词： frequency comb,spectroscopy,Quantum cascade laser,metrology,terahertz
更新于2025-09-23 15:21:01
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Terahertz electromagnetic waves radiated from coherent longitudinal optical (LO) phonons and LO-phonon plasmon coupled modes in (001)-, (110)-, and (111)-oriented semi-insulating GaAs single crystals
摘要： We report on terahertz electromagnetic waves from coherent longitudinal optical (LO) phonons and coherent LO-phonon plasmon coupled (LOPC) modes in (001)-, (110)-, and (111)-oriented semi-insulating GaAs single crystals. The coherent LO phonons and coherent LOPC modes are observed in the three samples. In contrast, coherent transverse optical (TO) phonons are not observed in the (110)- and (111)-oriented samples in spite of that the TO phonon is the Raman active mode. We conclude that only the coherent longitudinal oscillating polarization such as coherent LO phonons and coherent LOPC modes radiate the terahertz wave and that the Raman selection rule does not contribute to the terahertz-wave-radiation process. The photogenerated electron-density dependence of the frequencies of the coherent LOPC mode is almost the same in the three samples. This ?nding indicates that the coupling of the LO phonon with the plasmon is not in?uenced by the surface orientations of the three samples.
关键词： coherent LO-phonon plasmon coupled mode,coherent longitudinal optical (LO) phonon,terahertz time-domain spectroscopy,coherent transverse optical phonon,ultrafast phenomena,Raman scattering effect
更新于2025-09-23 15:21:01
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Active broadband manipulation of terahertz photonic spin based on gyrotropic Pancharatnam-Berry metasurface
摘要： Controlling terahertz (THz) waves, especially the polarization state and deflection angle, is important in THz application systems. But most of conventional THz metasurfaces have limitations in efficiency and working bandwidth. Although Pancharatnam-Berry excellent manipulation for the circular polarized (CP) waves (or called photonic spin states) without phase dispersion, there is still challenge in active controlling. Here, we developed a magnetically tunable gyrotropic P-B metasurface by combining the gyroelectric semiconductor InSb and the P-B elements, which obtain two important effects: One is the active photonic spin Hall effect, which controls the conversion between two CP states and the deflection in space. A broadband working frequency of 1.02~1.7 THz is obtained with the sweeping deflection angle from 36.6° to 83.5° and the highest efficiency of over 70%. The other is photonic spin filter effect, which reflects one CP state but absorb the other orthogonal CP state, realizing nonreciprocal absorption with the isolation of 24 dB. This active, high efficiency and broadband P-B metasurface opens a new way in manipulation of the THz wave propagation and polarization states in both space and frequency domains.
关键词： Magneto-optical device,terahertz,subwavelength structure
更新于2025-09-23 15:21:01
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A Terahertz Traveling-Wave Tube Based on Defect Photonic Crystal Waveguide
摘要： A defect photonic crystal waveguide (DPCW) is presented as a slow-wave structure (SWS) for terahertz (THz) traveling-wave tube (TWT). Due to the characteristics of DPCW, the mode competition and backward wave are greatly depressed, improving the stability of TWT. The DPCW SWS has ?at dispersion characterization and high interaction impedance at 220 GHz. Simulation results show that saturated output power of 12.1 W, corresponding to a gain of 24.3 dB, and the 3-dB gain ripple within 20 GHz can be achieved at the center frequency of 220 GHz. The DPCW-TWT has a low working voltage at 9.52 kV compared to that of folded waveguide (FWG) SWS in this frequency band. The proposed DPCW for the THz regime is easy to fabricate and assemble using the modern fabrication processing technology.
关键词： terahertz,Defect photonic crystal waveguide (DPCW),traveling-wave tube (TWT),slow-wave structure (SWS)
更新于2025-09-23 15:21:01
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Breakdown of Pauli spin blockade by phonon irradiation in a GaAs double quantum dot
摘要： In this letter, we report initial experimental results which provide the foundation for low-terahertz (low-THz) radar imagery for outdoor unstructured scenarios as expected in automotive sensing. The requirements and speci?cations for a low-THz single imaging radar sensor are brie?y outlined. The imaging capabilities of frequency-modulated continuous-wave (FMCW) radar operating at 150 GHz are discussed. A comparison of experimental images of on-road and off- road scenarios made by a 150-GHz FMCW radar and a reference 30-GHz stepped-frequency radar is implemented, and their performance is analyzed.
关键词： low terahertz (low-THz),Imaging radar
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Shunt Resistance Relation to Power Loss due to Potential Induced Degradation in Crystalline Photovoltaic Cells
摘要： In this letter, we report initial experimental results which provide the foundation for low-terahertz (low-THz) radar imagery for outdoor unstructured scenarios as expected in automotive sensing. The requirements and speci?cations for a low-THz single imaging radar sensor are brie?y outlined. The imaging capabilities of frequency-modulated continuous-wave (FMCW) radar operating at 150 GHz are discussed. A comparison of experimental images of on-road and off- road scenarios made by a 150-GHz FMCW radar and a reference 30-GHz stepped-frequency radar is implemented, and their performance is analyzed.
关键词： low terahertz (low-THz),Imaging radar
更新于2025-09-23 15:21:01
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Tunable Terahertz Graphene-Based Absorber Design Method Based on a Circuit Model Approach
摘要： In this paper, a simple, fast, and novel method for designing a tunable terahertz absorber with arbitrary central frequency and desired fractional bandwidth is presented. The proposed absorber consists of a single layer periodic array of graphene ribbons (PAGRs), placed a quarter wavelength from a metallic ground, separated by a dielectric material. An analytical circuit model of the terahertz absorber is used to obtain analytical expressions for the input impedance of the proposed device. Then, a simple expression for determining the value of capacitance and the resonance conditions of the RLC circuit is used to achieve a terahertz absorber with arbitrary central frequency and desired fractional bandwidth. The proposed method is applicable for the design of both narrowband and broadband absorbers, with only one layer of graphene ribbons. Also, the presented method is applicable for designing ultra-wideband absorbers using multiple layered PAGRs. Full-wave numerical simulation is performed to verify the accuracy and validity of the presented method. Excellent performance of the proposed method in terms of computation time and memory resource and providing the desired terahertz absorber characteristics shows that our method is promising as a design approach for sensing, imaging and ?ltering applications.
关键词： circuit model,graphene,Terahertz absorber,transmission line method,tunable bandwidth
更新于2025-09-23 15:21:01
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Optimization of PBG-Waveguides for Terahertz-Driven Electron Acceleration
摘要： The properties of 2-D photonic bandgap dielectric structures, also called photonic crystals, are numerically investigated to assist the design of waveguides for terahertz (THz)-driven linear electron acceleration. Given the broadband nature of the driving pulses in THz acceleration regimes, one design aim is to maximize the photonic bandgap width to allow propagation of the relevant frequencies within the photonic crystal linear defect waveguide. The proposed design is optimized to provide the best compromise between effective acceleration bandwidth and strong beam–wave interaction at the synchronism central frequency. Considerations on achieved acceleration bandwidth, accelerating voltage, and surface magnetic field are given to compare the proposed geometry to one of the main counterparts in the literature—the dielectric-lined waveguide.
关键词： Photonic crystals,terahertz (THz) electron acceleration,photonic-bandgap waveguides (PBG-Ws)
更新于2025-09-23 15:21:01