The terahertz (THz) frequency range is electromagnetic radiation in the range from 0.1 to 10 THz, which has high potential for use in non-destructive testing and control of the moisture content of objects. For a long time there was no elemental base of elements (receivers, transmitters, modulators, etc.) to work in this range. At the moment, existing detectors are made according to difficult and inaccessible technologies (like as molecular-beam epitaxy). In this paper, terahertz detector based on a thin-film structured thermoelectric material (solid solution of bismuth-antimony with a concentration of antimony of 12%) and copper contacts on a mica substrate was numerically demonstrated.
Efficient devices for control properties of electromagnetic waves are essential for the development of terahertz (THz) technologies. But despite the great progress achieved in a study of graphene, the influence of the number of graphene layers on its properties in the THz frequency range has not yet been sufficiently studied. In this work, we experimentally studied properties of multilayer graphene (MLG) films in the frequency range 0.2–0.8 THz, at a room temperature, and a relative humidity of 40%. Using our custom-made THz time-domain spectroscopic polarimetry system, we obtained spectra of the complex relative permittivity and the electrical conductance of the chemical vapor deposition graphene with ∼14, ∼40, and ∼76 layers of graphene on glass substrates. It is shown that the conductance increases nonlinearly with an increase in the graphene layer number and reaches, for ∼76 layers, 0.06 S for the real, and 0.03 S for the imaginary part, respectively.
Dynamical manipulation of electromagnetic radiation in arbitrary manner is achievable through metasurface utilization. Significant issue for practical applications of metasurfaces is in solving inverse problem, i.e. prediction of metasurface pattern dimensions in accordance to the desired electromagnetic response. In this work, we propose the approach based on equivalent circuit model enabling to connect resonant features of metasurface with its geometry dimensional parameters.
The influence of antimony content x and a film thickness on dynamical terahertz conductivity and galvanomagnetic properties of thin-film bismuth antimonides Bi1-xSbx at room temperature is studied in this work by means of terahertz time-domain spectroscopy and galvanomagnetic measurements. It is shown that thin bismuth-antimony films have tunable optical response in the THz frequency range. The hyperbolic permittivity dispersion of an effective film-on-substrate structure is also reported. The studied thin-film materials can be applied in detection of terahertz radiation and in terahertz filtering, modulation, phase and polarization shifting, in sensing, imaging and communication systems which work at normal conditions.
In this work, we propose and theoretically investigate the first dynamically tunable metasurface based on new twodimensional (2D) material - multi-layer graphene (MLG). As a basis for metasurface development, the results of experimental studies in THz frequency band of 80-layered graphene on dielectric substrate under external optical pumping were used. The metasurface consist of the Polymethylpentene (TPX) substrate and cross-shaped MLG pattern. In addition, the structure of the metasurface is very simple and can be fabricated by chemical vapor deposition and laser engraving. Proposed non-metallic metasurface is high-potential candidate for designing an active THz devises.
In this work, we study infrared optical pump-induced changes in terahertz conductivity of multi-layer graphene on a silicon substrate using terahertz time-domain spectroscopy. Results indicate that the conductivity and optical parameters of investigated material strongly depend on a pumping intensity and the presence of FeCl3 molecules intercalation. The findings are helpful for determining the most optically tunable material towards designing of optically controllable terahertz devices based on new two-dimensional material beyond graphene monolayer.
We propose a high-Q optically tunable terahertz (THz) filter consisting of subwavelength multilayer graphene/ dielectric/metal asymmetric square split-ring resonators (SRR) within a unit cell. The obtained simulation results demonstrate that Fano resonance can be efficiently modulated under IR-radiation of different intensity value. The modulation depth of Fano resonance can achieve about 60% under the maximum considered pumping intensity (corresponding to 0.4 eV of Fermi energy) with the Q-factor of about 135. The proposed metasurface provides narrow filtering of incident light as well as sensing applications.
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