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Study on Detecting Dielectric Properties of Typical Electrical Insulation Materials by Terahertz Wave Spectroscopy
摘要： The dielectric properties of the electrical insulation materials is of great importance to the safe operation of the power system. As a promising technique in the field of material testing and with the very adaptive physical modeling of wave transmission process, terahertz wave was used to measure the dielectric properties of five commonly used insulation materials by two methods in this paper. When excluding the echo pulse from the reference signal and the sample signal, a better signal-noise ratio and a wider effective frequency band of spectrums can be obtained. Alternatively, the dielectric properties can also be achieved by separating the main pulse and echo pulse from the sample signal. The latter method makes the sampling of reference signal unnecessary. Furthermore, the dielectric properties of materials were also measured on a relative lower frequency band (1Hz-1MHz) by the broadband dielectric spectrometer. Compared with a relatively lower frequency band, due to the polarization, the dielectric constant of the tested insulation materials was lower on the terahertz band while the dielectric loss tangent was generally higher except the epoxy resin.
关键词： Dielectric properties,Terahertz wave,Insulation materials,Broadband dielectric spectrometer
更新于2025-09-11 14:15:04
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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) - Linear to Circular Polarization Conversion of Terahertz Wave Using Metallic Helix Array
摘要： We developed a 2D array of 3D metallic helix which converts linearly polarized terahertz (THz) wave into circularly polarized THz wave and acts as a broadband THz wave polarizer. It covers the frequency range from 140 GHz to 250 GHz, close to one octave. We made two different arrays which consist of left-handed and right-handed metallic helices and we confirmed that these arrays change the linearly polarized THz wave into right-hand and left-hand circularly polarized THz wave respectively.
关键词： terahertz wave,metallic helix array,broadband polarizer,polarization conversion
更新于2025-09-10 09:29:36
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Photoconductive antennas based on epitaxial films In <sub/>0.5</sub> Ga <sub/>0.5</sub> As on GaAs (1?1?1)A and (1?0?0)A substrates with a metamorphic buffer
摘要： The terahertz (THz) wave generation by the spiral photoconductive antennas fabricated on the low-temperature and high-temperature grown undoped and Si-doped In0.5Ga0.5As films is studied by the terahertz time-domain spectroscopy method. The In0.5Ga0.5As layers were grown by molecular beam epitaxy on GaAs substrates with (1 0 0) and (1 1 1) A crystallographic orientations utilizing step-graded InxGa1?xAs metamorphic buffer. The antennas are excited by radiation of Er3+-fiber laser at 1.56 μm wavelength in two regimes: with pulse durations of 2.5 ps or 100 fs. It is found that the THz wave generation is 3–4 times more effective in the case of InGaAs-based antennas on (1 1 1)A GaAs substrates as compared to the (1 0 0) substrates. Power-voltage characteristic of the LT-InGaAs antenna up to and beyond threshold breakdown voltage are reported.
关键词： time-domain spectroscopy,terahertz wave generation,photoconductive antenna,GaAs (1 1 1)A,InGaAs,molecular beam epitaxy
更新于2025-09-09 09:28:46