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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - A Graphene-Based Tunable THz Metamaterial Absorber
摘要： A graphene-based tunable THz metamaterial absorber is presented in this paper. The proposed absorber is a periodical structure with the unit cell composed of four square gold patches on single-layered graphene, which are placed on a dielectric spacer supported by a gold bottom layer. Simulation results indicate that the absorption frequency can be tuned by varying the chemical potential of graphene through controlling of the electrostatic gating or the geometry size of the gold patch. By introducing more gold patches with different size into the unit cell, we can obviously extend the absorption bandwidth to achieve a broadband absorber.
关键词： broadband,THz,metamaterial absorber,tunable,graphene
更新于2025-09-04 15:30:14
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Magnetoconductivity and Terahertz Response of a HgCdTe Epitaxial Layer
摘要： An epitaxial layer of HgCdTe—a THz detector—was studied in magnetotransmission, magnetoconductivity and magnetophotoconductivity experiments at cryogenic temperatures. In the optical measurements, monochromatic excitation with photon frequency ranging from 0.05 THz to 2.5 THz was used. We show a resonant response of the detector at magnetic ?elds as small as 10 mT with the width of the resonant line equal to about 5 mT. Application of a circular polarizer at 2.5 THz measurements allowed for con?rming selection rules predicted by the theory of optical transitions in a narrow-gap semiconductor and to estimate the band-gap to be equal to about 4.5 meV. The magnetoconductivity tensor was determined as a function of magnetic ?eld and temperature 2 K < T < 120 K and analysed with a standard one-carrier conductivity model and the mobility spectrum technique. The sample showed n-type conductivity at all temperatures. At temperatures above about 30 K, conductivity was found to be reasonably described by the one-carrier model. At lower temperatures, this description is not accurate. The algorithm of the spectrum of mobility applied to data measured below 30 K showed presence of three types of carriers which were tentatively interpreted as electrons, light holes and heavy holes. The mobility of electrons and light holes is of the order of 106 cm2/Vs at the lowest temperatures. Magnetophotoconductivity experiments allowed for proposing a detector working at 2 K and 50 mT with a ?at response between 0.05 THz and 2.5 THz.
关键词： HgCdTe,THz magnetospectroscopy,magnetoconductivity
更新于2025-09-04 15:30:14
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Highly Sensitive Detection of 4-Methylimidazole Using a Terahertz Metamaterial
摘要： In this study, we demonstrated a highly sensitive detection method of 4-methylimidazole (4-MeI), a carcinogenic material, by using a terahertz (THz) metamaterial at a THz region. The THz metamaterials were fabricated with a metal array, using an electric-field-coupled inductor-capacitor (ELC) resonator structure, and a finite-difference time-domain (FDTD) simulation showed good agreement with the experimental results. We measured the THz spectra of the metamaterials to detect the 4-MeI concentrations of 0, 1, 2, 5, 10, 15, and 20 mg/L. The resonance frequency of the metamaterial was shifted by, approximately, 8 GHz and transmittance at the resonance frequency increased to 2 × 10?3, as the concentration was increased, up to 20 mg/L. Our study provides new insight into the application of metamaterials in detecting carcinogens, using a THz technique.
关键词： THz spectroscopy,carcinogen detection,4-methylimidazole,metamaterial
更新于2025-09-04 15:30:14