Rasulova GK, Pentin IV, Goltsman GN. Terahertz emission from a weakly-coupled GaAs/AlGaAs superlattice biased into three different modes of current self-oscillations. AIP Advances. 2019;9(10):105220.
Abstract: Radio-frequency modulated terahertz (THz) emission power from weakly-coupled GaAs/AlGaAs superlattice (SL) has been increased by parallel connection of several SL mesas. Each SL mesa is a self-oscillator with its own oscillation frequency and mode. In coupled non-identical SL mesas biased at different voltages within the hysteresis loop the chaotic, quasiperiodic and frequency-locked modes of self-oscillations of current arise. THz emission was detected when three connected in parallel SL mesas were biased into the frequency-locked and quasiperiodic modes of self-oscillations of current, while in the chaotic mode of those it falls to the noise level.
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Antipov S, Trifonov A, Krause S, Meledin D, Kaurova N, Rudzinski M, et al. Improved bandwidth of a 2 THz hot-electron bolometer heterodyne mixer fabricated on sapphire with a GaN buffer layer. Supercond Sci Technol. 2019;32(7):075003.
Abstract: We report on the signal-to-noise and gain bandwidth of a niobium nitride (NbN) hot-electron bolometer (HEB) mixer at 2 THz fabricated on a sapphire substrate with a GaN buffer layer. Two mixers with different DC properties and geometrical dimensions were studied and they demonstrated very close bandwidth performance. The signal-to-noise bandwidth is increased to 8 GHz in comparison to the previous results, obtained without a buffer-layer. The data were taken in a quasi-optical system with the use of the signal-to-noise method, which is close to the signal levels used in actual astrophysical observations. We find an increase of the gain bandwidth to 5 GHz. The results indicate that prior results obtained on a substrate of crystalline GaN can also be obtained on a conventional sapphire substrate with a few micron MOCVD-deposited GaN buffer-layer.
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Ren Y, Zhang DX, Zhou KM, Miao W, Zhang W, Shi SC, et al. 10.6 μm heterodyne receiver based on a superconducting hot-electron bolometer mixer and a quantum cascade laser. AIP Advances. 2019;9(7):075307.
Abstract: We report on the development of a heterodyne receiver at mid-infrared wavelength for high-resolution spectroscopy applications. The receiver employs a superconducting NbN hot electron bolometer as a mixer and a room temperature distributed feedback quantum cascade laser operating at 10.6 μm (28.2 THz) as a local oscillator. The stabilization of the heterodyne receiver has been achieved using a feedback loop controlling the output power of the laser. Improved Allan variance times as well as a double sideband receiver noise temperature of 5000 K and a noise bandwidth of 2.8 GHz of the receiver system are demonstrated.
The work is supported in part by the National Key R&D Program of China under Grant 2018YFA0404701, by the CAS program under Grant QYZDJ-SSW-SLH043 and GJJSTD20180003, by the National Natural Science Foundation of China (NSFC) under Grant 11773083, by the “Hundred Talents Program” of the “Pioneer Initiative”, and in part by the CAS Key Lab for Radio Astronomy.
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Kitaeva GK, Kornienko VV, Kuznetsov KA, Pentin IV, Smirnov KV, Vakhtomin YB. Direct detection of the idler THz radiation generated by spontaneous parametric down-conversion. Opt Lett. 2019;44(5):1198–201.
Abstract: We study parametric down-conversion (PDC) of optical laser radiation in the strongly frequency non-degenerate regime which is promising for the generation of quantum-correlated pairs of extremely different spectral ranges, the optical and the terahertz (THz) ones. The possibility to detect tenuous THz-frequency photon fluxes generated under low-gain spontaneous PDC is demonstrated using a hot electron bolometer. Then experimental dependences of the THz radiation power on the detection angle and on the pump intensity are analyzed.
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Tretyakov IV, Anfertyev VA, Revin LS, Kaurova NS, Voronov BM, Vaks VL, et al. Sensitivity and resolution of a heterodyne receiver based on the NbN HEB mixer with a quantum-cascade laser as a local oscillator. Radiophys Quant Electron. 2018;60(12):988–92.
Abstract: We present the results of experimental studies of the basic characteristics and operation features of a terahertz heterodyne detector based on the superconducting NbN HEB mixer and a quantum cascade laser as a local oscillator operating at a frequency of 2.02 THz. The measured noise temperature of such a mixer amounted to 1500 K. The spectral resolution of the detector is determined by the width of the local-oscillator spectral line whose measured value does not exceed 1 MHz. The quantum-cascade laser could be linearly tuned with respect to frequency with the coefficient 7.2 MHz/mA within the limits of the current oscillation bandwidth.
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