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Bulk films and heterostructures based on HgCdTe compounds can be engineered to fabricate “gapped-at-will” structures. Therefore, 1D [1], 2D [2] and even 3D [3] massless particles can be observed in topological phase transitions driven by intrinsic (quantum well thickness, Cd content) and external (magnetic field, temperature or pressure) physical parameters. So far, the phases of 2D [1] and 3D [4]...
Ac conductivity and dielectric permittivity of bovine serum albumin, cytochrome c and extracellular matrix synthesized by electrogenic bacteria Shewanella oneidensis MR-1 are measured at frequencies 1–1012 Hz and temperatures 10–300 K. Two types of conductivity mechanisms are observed as well as nearly constant loss (NCL) phenomenon, universal dielectric response (UDR) and signatures of boson peak...
Tuning the band structure of a topological insulator is of interest for developing electronic devices or superconducting devices. Here we report the strain-dependent results for Bi2Se3 films of various thicknesses that are grown via a self-organized ordering process. From the UV photoemission/inverse photoemission spectroscopy (UPS/IPES) results, ab initio calculations and THz-TDS data, significant...
We device plasmonic, bolometric and thermoelectric antenna-coupled Terahertz photodetectors based on black phosphorus and hybrid van der Walls heterostructures, showing 20000 signal to noise ratios and 100pW/Hz1/2 noise equivalent powers in the 0.3–3 THz frequency range.
In this newly reported discovery, common THz absorption signatures from lactose and biotin are found to significantly “red-shift” in frequency with increase in hydration, especially in the hydration range of ∼10 to 20% by weight. Interestingly, the associated linewidth (i.e., FWHM) sometimes broadens (consistent with the Lorentzian oscillator model) as in biotin, but other times narrows somewhat,...
In this work we investigate and compare the features of the THz generation process caused by an optical breakdown of air both in a “filament” and “micro-plasma” regimes. We explore efficiency, a spatial and spectral distributions of terahertz radiation in each case.
We performed spectroscopic studies of water-containing beryl crystals. At terahertz frequencies, we observed a strongly temperature-dependent spectral feature, corresponding to a collective excitation caused by dipole-dipole interactions between separate H2O molecules. We associate the excitation with a soft mode signaling an incipient ferroelectric state within the water molecular subsystem. Single-particle...
By numerical simulations, we investigate the behavior of the current photoresponse of InGaAs high electron mobility transistors (HEMTs) submitted to THz radiations. By increasing the incoming wave power density, the response of the device is shown to saturate, in agreement with experimental results. This limitation of the detection features is shown to be due to electron heating.
This study investigates the linear behavior of the TM modes for gyrotron operation and reveals that certain TM modes might be suitable for gyrotrons — ECM based devices. In addition, non-linear model shows that for a fixed field profile the efficiency could be as high as that of the transverse electric (TE) modes.
Electromagnetically induced transmission (EIT) in THz domain is studied in Dolmen structures. The effect of dipole in exciting the otherwise dark quadrupole mode and the interaction of a 2nd dipole in controlling the EIT peak are studied. We show broad EIT peak in Dolmen as well as two EIT peaks and vanishing of EIT peak by varying the position of a 2nd dipole to form a ring like structure.
We report the observation of multiple polariton branches in an ultra-strongly coupled system of Landau level transitions in strained Ge quantum wells (sGe QWs) and a THz metamaterial. The sGe QW system shows narrow spin-split heavy-hole cyclotron resonances and thus leads to multiple cyclotrons. The coupled system can be described by an expanded ultra-strong coupling Hamiltonian including all oscillators...
We designed and manufactured terahertz (THz) waveguide high-pass filters (HPFs) with cutoff frequencies exceeding those of known analogs. These HPFs will be used in a proposed system for measuring spectra of single THz pulses or of the pulses radiated with a low-repetition rate. The system restores the pulse spectrum from measured amplitudes of the initial pulse and of the pulses, transmitted through...
In this study we demonstrate compressive sensing imaging with a unique graphene based optoelectronic device which allows us to modulate the THz field through an array of columns or rows distributed throughout its face.
A system where a graphene sheet is placed above a topologically insulating material is investigated when hopping is allowed between the two surfaces. The optical conductivity of such a system presents interesting features that do not occur in the two constituent surfaces separately.
We presented a comprehensive study on widely tunable and monochromatic THz-wave generation with homemade organic crystals DSTMS and OH1. A tuning range of 0.02–20 THz was achieved. Parameter dependence of THz output was investigated. The experimental results were well explained based on theoretical analysis.
Research activity on development of various types of gyro-devices at the Institute of Applied Physics of Russian Academy of Sciences (IAP RAS) and at industrial company GYCOM Ltd is presented. Recent results of the development are illustrated by a number of examples of fabricated and tested gyrotrons-oscillators and gyro-amplifiers operating at very different frequencies.
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