- 标题
- 摘要
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- 实验方案
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Laser-ablated silicon in the frequency range of 0.1 to 4.7 THz
摘要： The optical performance of high-resistivity silicon with a laser-ablated surface was studied in the transmission mode in the frequency range of 0.1-4.7 THz. A reciprocal relationship between the transmission brightness and the surface roughness was observed at discrete THz frequencies. The measured dispersion was reproduced by the THz wave scattering theory using an effective refractive index model. No significant differences between the samples processed either with ps- or ns-duration laser pulses in ambient air or in argon enriched atmosphere were found in the THz regime. It was demonstrated that the majority of optical losses of the silicon with the laser modified surface were due to the scattering of THz waves and not due to the absorption in silicon-compounds formed during the laser ablation.
关键词： terahertz waves,diffraction,laser-ablation,scattering
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Low-Voltage Tuning of the Terahertz Passband Transmission using a Tungsten-Doped VO <sub/>2</sub> -Based Metamaterial
摘要： Vanadium dioxide (VO2), which exhibits a semiconductor-metal phase transition at temperatures close to room temperature of 340 K, has been used as a suitable material for carrying out metamaterials that are artificially designed assemblies consisting of subwavelength lattice arrays with unnatural electromagnetic properties in applications such as filters, modulators, and absorbers in the terahertz (THz) frequency range [1-3]. We have demonstrated that the square-loop metamaterial (SLM) can precisely control the amplitude in the range of 0.3–0.6 THz at low voltages below 2 V, when the SLM is combined with tungsten (W)-doped VO2 film. Unlike an undoped-VO2-film-based device with a digital-type switching amplitude response, the device with a 1.2 at.% W-doped VO2 film performed a modulation depth (MD) of 0.72 @0.4 THz, where MD = ((E^2@0V - E^2@2V)/E^2@0V), for transmission of the THz wave in a polarization state perpendicular to the voltage bias line (the direction of the transmitted linear-polarized THz electric-field perpendicular to the voltage bias line pattern of the SLM structure). The proposed metamaterials in the form of the double-square structure connected together can define the desired passband by the resonances derived from each square-loop. In addition, the transmittance of the THz wave was continuously tuned by using the W-doped VO2 thin film formed by the sol-gel method as a substrate. These phase-change material-coupled metamaterial structures can be utilized in analog/digital modulators and bandpass filter applications in the THz frequency region.
关键词： tungsten-doped,low-voltage tuning,metamaterial,terahertz,Vanadium dioxide
更新于2025-09-11 14:15:04
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Generation of a Few Cycle Terahertz Pulse in Aperiodically Poled Lithium Niobate by Sequence of Pump Pulses
摘要： It is shown that chirped aperiodically poled lithium niobate crystal is capable to generate powerful THz pulses with controllable number of THz field oscillations (from nearly single- to multi-cycles), when it is pumped by sequence of femtosecond laser pulses with chirped delays between adjacent pulses. The peak electric field strength of about 0.3 MV/cm (for non-focused THz beam) is predicted if intensity of each pump pulse in the sequence is 20 GW/cm2.
关键词： Optical rectification,Aperiodically poled lithium niobate,Terahertz pulse,Femtosecond laser pulses
更新于2025-09-11 14:15:04
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[IEEE 2019 5th Conference on Knowledge Based Engineering and Innovation (KBEI) - Tehran, Iran (2019.2.28-2019.3.1)] 2019 5th Conference on Knowledge Based Engineering and Innovation (KBEI) - A Triple-Band THz Metamaterial Absorber Based on Symmetrical Split Rings
摘要： A simple pattern of a triple band terahertz (THz) absorber is presented. This absorber formed by only triple symmetrical split rings backed with a solid ground layer which is separated by a dielectric layer substrate. It is investigated that the presented absorber has three different absorption bands in which the average of the peaks is close to 96%. Results reveal that the absorption bandwidth of the presented design is insensitive to wave incident angle. In addition, in order to enhance the absorption peaks, a new method is introduced which is based on the difference of split rings thickness. Owing to the simple structure of the proposed absorber, the fabrication process can be quite easy. Therefore, the proposed THz absorber is able to perform in applications such as sensing, detection, and imaging.
关键词： split rings structure,metamaterial,triple band,terahertz (THz),absorber
更新于2025-09-11 14:15:04
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Terahertz Selective Emission Enhancement from a Metasurface-Coupled Photoconductive Emitter in Quasi-Near-Field Zone
摘要： We present a THz emission enhancement of 41 times at 0.92 THz from a metasurface made of T-shaped resonators excited in a quasi-near-field zone. Such a metasurface has an intrinsic transmission minimum with Q factor of 4 at 1.25 THz under far-field excitation. When this metasurface is coupled onto the backside of a 625-μm-thick photoconductive emitter, the metasurface is below the Fraunhofer distance to the excitation source. As such, one broad enhancement around 0.47 THz and another extremely narrow enhancement at 0.92 THz in the emission spectrum are observed owing to a quasi-near-field excitation. Theoretically, the Q factor of the latter is up to 307, which is limited by the spectral resolution in experiment. The numerical simulations indicate that the T-shaped resonators serve as an array of plasmonic antennas resulting in the aforementioned emission enhancement of THz radiation.
关键词： Terahertz,Metamaterial,Quality factor,Quasi-near-field
更新于2025-09-11 14:15:04
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Terahertz emission from a weakly-coupled GaAs/AlGaAs superlattice biased into three different modes of current self-oscillations
摘要： Radio-frequency modulated terahertz (THz) emission power from weakly-coupled GaAs/AlGaAs superlattice (SL) has been increased by parallel connection of several SL mesas. Each SL mesa is a self-oscillator with its own oscillation frequency and mode. In coupled non-identical SL mesas biased at different voltages within the hysteresis loop the chaotic, quasiperiodic and frequency-locked modes of self-oscillations of current arise. THz emission was detected when three connected in parallel SL mesas were biased into the frequency-locked and quasiperiodic modes of self-oscillations of current, while in the chaotic mode of those it falls to the noise level.
关键词： current self-oscillations,quasiperiodic mode,terahertz emission,frequency-locked mode,GaAs/AlGaAs superlattice,chaotic mode
更新于2025-09-11 14:15:04
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Design and Measurement of a Terahertz Double Staggered Grating Waveguide With an Arc-Shaped Beam Tunnel
摘要： A millimeter-waveband double staggered grating waveguide (DSGW) with an arc-shaped beam tunnel was previously proposed for sheet beam traveling wave tubes. In this article, the design, fabrication, and cold test of a terahertz band DSGW with an arc-shaped beam tunnel are presented. Simulations demonstrated that the novel DSGW would have a higher coupling impedance and a better beam wave interaction in comparison to the conventional DSGW with a linear-shaped beam tunnel. Beam wave interaction simulations showed that the output power and the electronic efficiency, respectively, increased from ～420 W to ～580 W and from 7.0% to 9.3% at 240 GHz. These two kinds of DSGWs were fabricated by using the nanocomputer numerical control (CNC) milling and wire cutting techniques, and their performances were cold tested by using a vector network analyzer. The measurement results were in good agreement with the simulations and demonstrated that both the traditional and novel DSGWs achieved a wide frequency bandwidth of ～40 GHz (0.22–0.26 THz) with a transmission coefficient S21 better than ?2.7/?3.0 dB and a reflection coefficient S11 lower than ?13.0/?15.7 dB, respectively.
关键词： terahertz radiation,sheet electron beam (SEB) devices,Arc-shaped beam tunnel,double staggered grating waveguide (DSGW)
更新于2025-09-11 14:15:04
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[IEEE 2019 Second International Workshop on Mobile Terahertz Systems (IWMTS) - Bad Neuenahr, Germany (2019.7.1-2019.7.3)] 2019 Second International Workshop on Mobile Terahertz Systems (IWMTS) - Flexible and Wearable Graphene-based Terahertz Antenna for Body-Centric Applications
摘要： This paper presents a graphene-based wearable antenna operating in the terahertz frequency range. Graphene with its highly attractive electronic properties, and modern manufacturing techniques can yield antennas that are not only flexible but efficient and low-profile, suited for terahertz applications. The graphene antenna investigated here has a resonant frequency of 0.647 THz. The performance of the antenna is evaluated on-body and in free space using three layers of human skin. Simulated results show that the proposed antenna has a bandwidth of 20 GHz and offers a radiation efficiency of 96% in free space and 50% on the body, with respective gains of 7.8 dB and 7dB. The small and flexible structure of the antenna along with excellent impedance matching, high bandwidth, and gain, and good efficiency makes it an appropriate candidate to short-range wireless communication in the vicinity of the human body.
关键词： graphene,flexible antenna,terahertz,wearables
更新于2025-09-11 14:15:04
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Circular-Photon-Drag-Effect-Induced Elliptically Polarized Terahertz Emission from Vertically Grown Graphene
摘要： Circular photon drag effect (CPDE) is important for helicity-dependent optoelectronic emitters and detectors yet is less studied in graphene due to the relatively weak light-matter interaction and is submerged by other nonlinear optical effects. We give experimental evidence of CPDE in vertically grown graphene (VGG) by terahertz (THz) emission spectroscopy. The emitted THz polarization states can be tuned to linear, left-handed, and right-handed elliptical polarizations by changing the helicity of the pump laser. Polarity reversal of the THz time-domain signal occurs with the opposite helicity of pump laser excitation due to the CPDE. Theory analysis suggests that both the linear photon drag effect and CPDE-induced transient photocurrents contribute to the THz emission from which the contribution weight of CPDE can be tuned by different elliptical states of the excitation light. The photon-helicity-dependent THz emission from VGG based on CPDE offers an alternative thought of graphene-based polarization sensitive THz sources for chiral analysis in the THz field.
关键词： Helicity-dependent,Terahertz emission,Polarization,Circular photon drag effect,Graphene
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP) - Bochum, Germany (2019.7.16-2019.7.18)] 2019 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP) - Pulse-resolved Data Acquisition System for THz Pump Laser Probe Experiments at TELBE using Super-radiant Terahertz Sources
摘要： the terahertz (THz) frequency range lies between the frequency range of radio and infrared. The development of suitable detectors, detection techniques, and sources for this frequency range has much interest over the past decade. THz pulses of sufficient strength that act as an excitation of dynamics in the matter have only been available, due to the development in 4th generation superconducting radiofrequency (SRF) technology. In the THz pump laser probe experiments the electric or magnetic field in the THz pump pulse acts as the excitation of dynamics in the matter. Ultra-short laser pulses then probe this dynamic in turn. In this contribution, we will outline the pulse-resolved data acquisition scheme of the TELBE user facility based on the characterization of a new class of accelerator-based light sources, which provide a unique combination of high pulse energies and high repetition rates.
关键词： Superradiant Terahertz Sources,Data Acquisition System,THz Radiation Detection Techniques,THz pump Laser Probe Experiments
更新于2025-09-11 14:15:04