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Terahertz (THz) imaging and tomography are modern imaging techniques allowing 2D and 3D inspection of objects over a broadband frequency range. However, the transfer of this technique to medical applications is limited to surface or subsurface inspection due to the large concentration of water molecules which are an intrinsic characteristic of biological tissues. Then, we report the results of investigations...
By utilizing a scattering-type scanning near-field optical microscope (s-SNOM) in mid-infrared (mid-IR) region, we studied nanoscale optical and thermal properties of the nanoporous graphene, that is an emerging type of carbon material. Nanoscale IR images revealed that the strained graphene near the nanopores emits less heat radiation, suggesting different absorption mechanism. The present findings...
We report on a new design of room-temperature terahertz quantum cascade lasers (THz QCLs) based on ZnMgSe/ZnSe material systems employing two-well design schemes with alternating quantum barrier heights and n-type delta-doping of the injector well. Our calculations show that this new THz QCLs achieves high optical gain at the emission frequency of 1.33 THz at room-temperature.
We describe time-domain terahertz spectroscopy measurements of the frequency-dependent conductivity in MnSi thin films. We find that at low temperatures and frequencies, the scattering rate is proportional to both the square of the temperature and the square of the frequency, as predicted Fermi liquid theory. Unlike measurements on many other systems, the prefactors for each functional dependence...
We study the role of complex scattering effects in transferred bi-layer and tri-layer CVD graphene, wherein the dynamics of intrinsic and photo-excited carriers is governed by interactions between adjacent layers. We observed non-Drude conductivity stemming from scattering in electrically connected systems; these effects being more pronounced at low temperatures. Dynamics of photo-excited carriers...
The terahertz optical response of a commensurate topologically insulator(TI)-graphene heterostructure is investigated. The interplay of interlayer hopping and topological band structure leads to additional selection rules for the inter band optical transition. The optical conductivity of such a system exhibits interesting features that do not occur in the two constituent surfaces separately. The transitions...
We proposed a novel planar meta-atom structure supporting higher order Fano resonances. The unit cell consists of a plasmonic defective corrugated metallic disk (CMD). The numerical and experimental results reveal that higher order Fano resonances can be generated at terahertz frequencies when symmetric CMD is broken with small defective angle. Such higher order Fano resonances result from the coupling...
Based on multiple quantum wells, we design a pumping-detection quantum cascade structure for the detection of terahertz (THz) radiation. In the structure, electrons are pumped by a mid-infrared (MIR) laser to an excited state, and then extracted by longitudinal optical (LO) phonon stairs. Within the stairs, THz absorption wells are designed. The LO-phonon stair extractor make electrons transport between...
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