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A feasibility of combining the gyrotron for dynamic nuclear polarization (DNP) application and the NMR spectrometer in the single superconducting magnet is considered. Simulations predict that a compact extremely low-voltage gyrotron (“gyrotrino”) can provide THz radiation at the frequency of 263 GHz required for DNP with power level of the order of 10 W.
We couple magneto-plasmons ultra-strongly to subwavelength split-ring resonator cavities, probed with THz time domain spectroscopy (TDS). In contrast to cyclotron-polaritons, the ultrastrong coupling regime is reached already at zero magnetic field. Further, the plasmon frequency ωρ is widely tunable using a gate and by changing the sample geometry. This thus allows to observe the transition from...
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 present ultra-broadband room temperature monolithic terahertz quantum cascade laser (QCL) sources based on intra-cavity difference frequency generation, emitting continuously more than one octave in frequency between 1.6 and 3.8 THz, with a peak output power of ∼0.2 mW. Broadband terahertz emission is realized by nonlinear mixing between single mode and multi mode spectra due to distributed feedback...
We demonstrate terahertz (THz) apertureless near-field microscopy exploiting the self-mixing effect in a quantum cascade laser (QCL). A THz wave is scattered by a sharp needle positioned above an object and coupled back into the QCL cavity resulting in detection of the THz near-field signal through the self-mixing effect. Using this technique we demonstrate two-dimensional imaging at 2.53 THz with...
We have demonstrated THz quantum-cascade metasurface vertical external cavity surface emitting lasers (VECSELs) using a variety of metasurfaces. The dependence of the laser spectrum on the metasurface design parameters is analyzed via simulation and experiment.
We describe two ways of the use in high-harmonic gyrotrons of quasi-regular cavities with short phase correctors. The first one is a significant improvement of the selectivity of the second-harmonic gyrotrons due to the suppression of parasitic near-cutoff fundamental-harmonic waves. The second approach is aimed to solve a typical problem of weakly-relativistic high-harmonics gyrotrons, namely, the...
Project of narrow-band 300 GHz / 500 kW radiation source operating in a quasi-continuous regime and aimed on modern plasma fusion applications is under development at ENEA (Frascati). As a solution of such source based on a moderately relativistic 500–700 keV/10–20 A electron beam cyclotron masers of different type are considered. The use of such a beam makes it possible to achieve high powers at...
Coaxial cavities with corrugated inserts and additional corrugations on the outer wall seem to have the potential for superior mode-selectivity and could be used to facilitate the development of multi-MW gyrotrons. This concept is used in this work to upgrade the design of an already manufactured 140-GHz coaxial gyrotron. A detailed sensitivity parametric study is performed to ensure mode stability...
We present modified circular patch resonators and discuss their potential for coupling to semiconductor heterostructures. We theoretically investigated these structures in combination with asymmetric QWs for second-harmonic generation (SHG) and parametric conversion (PC). The Q-factor of modes of the bare (empty) circular plasmonic resonator is proved to be at least 40 and a mode overlap factor of...
By sandwiching a single GaAs/AlGaAs QWIP into the subwavelength metal/dielectric/metal plasmonic cavity, the cut-off wavelength of the QWIP has been extended by about 8.35% whilst the dark current is kept unchanged. The reason is attributed to the localized surface plasmon cavity mode enhancement to the photo-responsivity at the wavelength of the cut-off tails.
Novel liquid-crystal tunable metamaterial devices for terahertz wave manipulation are designed and investigated. Deeply subwavelength layers of nematic materials are introduced in metal-liquid-crystal-metal cavities, leading to strong interaction of the THz wave with the liquid crystal anisotropy. The enhanced response in the liquid-crystal layer yields extensive tunability of the electromagnetic...
A Metal-Insulator-Metal (MIM) plasmonic optical microcavity is proposed to be integrated with an InP based single photon avalanche diode (SPAD). The MIM microcavity includes a large top metallic grating to couple incident light into the cavity and a small bottom metallic grating to couple the light into the APD, which provides a possibility to improve the SPAD's performance through decreasing the...
An Inverse Magnetron Injection Gun (IMIG) design is proposed for future conventional-type high-power gyrotrons. The design is deduced from the design for the KIT 2-MW, 170-GHz coaxial-cavity gyrotron prototype which has been published recently. As for the coaxial-cavity gyrotron IMIG, the inverse MIG design for the conventional hollow-type gyrotron is offering the possibility for compact geometry,...
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