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- 摘要
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- 实验方案
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Double-sided split-step MM-wave Fresnel lenses: design, fabrication and focal field measurements
摘要： Design, fabrication and focal field measurements of W-band Fresnel lenses to produce well-shaped Gaussian beams in the focal domain are presented. Two lenses, one of Teflon and another of Polyamide, have been compared in their performance with a double-sided Fresnel lens of different design, with full height of Fresnel steps. Experiments show that a good focusing ability of all the lenses is achieved. They produce the target beam according to the design. Yet, the lenses of split-step design are thinner, have lower insertion losses, and a greater focal depth as compared to more conventional Fresnel lenses.
关键词： focal fields,Fresnel lenses,Gaussian beam,MM-wave,THz applications
更新于2025-09-23 15:21:01
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Detection of Human Tumor Markers with THz Metamaterials
摘要： THz bioanalytical techniques are already proven as a viable tool for the label-free detection of biomolecules. But still, significant improvement of THz sensing techniques is needed to reach application relevant sensitivity levels. We present the label-free THz sensing of human tumor markers using a highly sensitive metamaterial based THz biosensor. High affinity binding of the specific protein to DNA is utilized for localized functionalization to further enhance the detection sensitivity.
关键词： tumor markers,DNA-protein interaction,THz sensing,metamaterials,biosensor
更新于2025-09-23 15:21:01
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All-carbon THz components based on laser-treated diamond
摘要： We report on fs laser structuring and graphitization of diamond and experimental characterization of its THz response. A full characterization of graphitized, conductive layer generated by laser irradiation is carried out by performing scanning-electron microscopy, Raman spectroscopy and electrical measurements. The transmittance of the laser textured diamond samples, both with the graphitic overlayer and after selective oxidizing etching, is analyzed in the (0.25 ÷ 6.0) THz spectral range. A significant selective absorption of the graphitized overlayer towards polarized THz radiation is demonstrated, which is associated to the formation of graphitic laser induced periodic surface structures. This anisotropy allows conceiving compact passive metasurfaces based on conductive/dielectric patterns on the diamond plate surface for the development of robust, lightweight and broadband THz optical components.
关键词： graphitic laser induced periodic surface structures,graphitization,electrical measurements,fs laser structuring,THz response,transmittance,THz optical components,polarized THz radiation,conductive layer,diamond,Raman spectroscopy,metasurfaces
更新于2025-09-23 15:19:57
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[IEEE 2019 Sixteenth International Conference on Wireless and Optical Communication Networks (WOCN) - Bhopal, India (2019.12.19-2019.12.21)] 2019 Sixteenth International Conference on Wireless and Optical Communication Networks (WOCN) - WIMAX Smart Grid Communication network for a Substation
摘要： This multidisciplinary paper reports on a research application-led study for predicting atmospheric attenuation, and tries to bridge the knowledge gap between applied engineering and atmospheric sciences. As a useful comparative baseline, this paper focuses specifically on atmospheric attenuation under pristine conditions, over the extended terahertz spectrum. Three well-known simulation software packages (‘HITRAN on the Web’, MODTRAN R(cid:13)4, and LBLRTM) are compared and contrasted. Techniques used for modeling atmospheric attenuation have been applied to investigate the resilience of (ultra-)wide fractional bandwidth applications to the effects of molecular absorption. Two extreme modeling scenarios are investigated: horizontal path links at sea level and Earth-space path links. It is shown by example that a basic software package (‘HITRAN on the Web’) can give good predictions with the former, whereas sophisticated simulation software (LBLRTM) is required for the latter. Finally, with molecular emission included, carrier-to-noise ratio fade margins can be calculated for the effects of line broadening due to changes in macroscopic atmospheric conditions with sub-1-THz ultra-narrow fractional bandwidth applications. Outdoors can be far from pristine, with additional atmospheric contributions only briefly introduced here; further discussion is beyond the scope of this paper, but relevant references have been cited.
关键词： molecular emission,atmospheric attenuation,carrier-to-noise,MODTRAN R(cid:13),THz Torch,HITRAN,thermal infrared,transmittance,THz,LBLRTM,molecular absorption
更新于2025-09-23 15:19:57
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Generation and modulation of terahertz gradient force in the interactions of two-color laser pulses with magnetized plasmas
摘要： Terahertz (THz) waves, as far-infrared light, offer new opportunities for the optical trapping and manipulation of single cells, in contrast to the other light sources. We present an efficient scheme to flexibly control multiple THz field distribution patterns generated by the laser–plasma interaction in a magnetized plasma. An analytical THz radiation field and two-dimensional particle-in-cell simulation are constructed to verify the feasibility of the scheme. Modulation of the THz gradient force and the energy flux by an asymmetrical THz field is investigated for the purpose of trapping and manipulating particles and cells. In particular, the stabilities of flexibly controlled THz radiation are investigated carefully in the form of the strong and short laser and super-strong magnetic field induced significant spatial structure instabilities and frequency instabilities of terahertz radiation.
关键词： Terahertz waves,laser–plasma interaction,optical trapping,magnetized plasmas,THz gradient force
更新于2025-09-23 15:19:57
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Terahertz shielding properties of aero-GaN
摘要： The electrodynamic properties of the first aero-material based on compound semiconductor, namely of Aero-GaN, in the terahertz frequency region are experimentally investigated. Spectra of complex dielectric permittivity, refractive index, surface impedance are measured at frequencies 4-100 cm-1 and in the temperature interval 4 – 300 K. The shielding properties are found based on experimental data. The aero-material shows excellent shielding effectiveness in the frequency range from 0.1 THz to 1.3 THz, exceeding 40 dB in a huge frequency bandwidth, which is of high interest for industrial applications. These results place the aero-GaN among the best THz shielding materials known today.
关键词： Complex dielectric permittivity,THz shielding,Aero-GaN
更新于2025-09-23 15:19:57
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[IEEE 2018 11th UK-Europe-China Workshop on Millimeter Waves and Terahertz Technologies (UCMMT) - HangZhou, China (2018.9.5-2018.9.7)] 2018 11th UK-Europe-China Workshop on Millimeter Waves and Terahertz Technologies (UCMMT) - Input coupling systems for terahertz gyro-TWAs
摘要： Input coupling systems for THz gyrotron traveling wave amplifiers (gyro-TWAs) are presented in this paper. These form one of the most critical parts of the gyro-TWA as it feeds the low power seed signal into the interaction circuit and incorrect design can lead to cessation of the amplification. The T-junction, multihole and multiarm coupler types were simulated in CST Microwave Studio and their optimized reflection and transmission characteristics, operating at a central frequency of 0.37 THz are presented. A scaled multiarm coupler, designed to then operate at 94 GHz, was manufactured and its microwave properties measured on a vector network analyser.
关键词： CST Microwave Studio,multihole coupler,THz gyro-TWAs,T-junction,multiarm coupler,input coupling systems
更新于2025-09-23 15:19:57
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Polarization Multiplexing Terahertz Metasurfaces through Spatial Femtosecond Lasera??Shaping Fabrication
摘要： Terahertz (THz) metasurface has emerged as a powerful technique to fully modulate the wavefronts of THz radiation. To improve the information storage capability and enhance the encryption security of THz metasurface holograms, smart metasurface designs, and fabrications for polarization multiplexing are essential. In this study, two kinds of polarization multiplexing THz metasurfaces are fabricated through the slit-based spatial modulation of femtosecond laser. Controllable elliptical aperture arrays can easily and flexibly be fabricated on gold films by adjusting the width and position of the slit combined with the laser pulse energy. Based on the Pancharatnam–Berry phase and amplitude modulation, respectively, THz metasurfaces, with two independent target phases or amplitude profiles, are obtained. A variety of information can be processed under different polarization states through these THz metasurfaces. This method allows flexible and efficient customization of THz metasurfaces because of the high-speed fabrication and reproducibility as well as precise control of elliptical apertures location on the surface.
关键词： spatial shaping,THz metasurface,femtosecond laser fabrication,polarization multiplexing
更新于2025-09-23 15:19:57
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Electromagnetic Physical Numerical Modeling of a GaN Distributed Transferred Electron Devicea??Based Planar Waveguide THz Oscillator
摘要： The radio frequency (RF) operation of a planar waveguide THz oscillator based on the distributed transferred electron device (DTED) is theoretically investigated by means of 2-D time-domain numerical physical modeling based on the self-consistent solution of the Maxwell and free electron energy-momentum macroscopic transport equations.
关键词： circuit design analysis,distributed transferred electron device (DTED),2-D time-domain electromagnetic physical numerical modeling,planar waveguide THz oscillator
更新于2025-09-23 15:19:57
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Ultra-long carrier lifetime in neutral graphene-hBN van der Waals heterostructures under mid-infrared illumination
摘要： Graphene/hBN heterostructures are promising active materials for devices in the THz domain, such as emitters and photodetectors based on interband transitions. Their performance requires long carrier lifetimes. However, carrier recombination processes in graphene possess sub-picosecond characteristic times for large non-equilibrium carrier densities at high energy. An additional channel has been recently demonstrated in graphene/hBN heterostructures by emission of hBN hyperbolic phonon polaritons (HPhP) with picosecond decay time. Here, we report on carrier lifetimes in graphene/hBN Zener-Klein transistors of ~30 ps for photoexcited carriers at low density and energy, using mid-infrared photoconductivity measurements. We further demonstrate the switching of carrier lifetime from ~30 ps (attributed to interband Auger) down to a few picoseconds upon ignition of HPhP relaxation at finite bias and/or with infrared excitation power. Our study opens interesting perspectives to exploit graphene/hBN heterostructures for THz lasing and highly sensitive THz photodetection as well as for phonon polariton optics.
关键词： photodetectors,mid-infrared,phonon polaritons,van der Waals heterostructures,THz,Graphene,carrier lifetime,hBN
更新于2025-09-23 15:19:57