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Author Baeva, E. M.; Titova, N. A.; Veyrat, L.; Sacépé, B.; Semenov, A. V.; Goltsman, G. N.; Kardakova, A. I.; Khrapai, V. S.
Title Thermal relaxation in metal films limited by diffuson lattice excitations of amorphous substrates Type Journal Article
Year 2021 Publication Phys. Rev. Applied Abbreviated Journal Phys. Rev. Applied
Volume (down) 15 Issue 5 Pages 054014
Keywords InOx, Au/Ni, NbN films
Abstract We examine the role of a silicon-based amorphous insulating substrate in the thermal relaxation in thin NbN, InOx, and Au/Ni films at temperatures above 5 K. The samples studied consist of metal bridges on an amorphous insulating layer lying on or suspended above a crystalline substrate. Noise thermometry is used to measure the electron temperature Te of the films as a function of Joule power per unit area P2D. In all samples, we observe a P2D∝Tne dependence, with exponent n≃2, which is inconsistent with both electron-phonon coupling and Kapitza thermal resistance. In suspended samples, the functional dependence of P2D(Te) on the length of the amorphous insulating layer is consistent with the linear temperature dependence of the thermal conductivity, which is related to lattice excitations (diffusons) for a phonon mean free path shorter than the dominant phonon wavelength. Our findings are important for understanding the operation of devices embedded in amorphous dielectrics.
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ISSN 2331-7019 ISBN Medium
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Notes Approved no
Call Number Serial 1769
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Author Semenov, A. D.; Hübers, Heinz-Wilhelm; Richter, H.; Birk, M.; Krocka, M.; Mair, U.; Vachtomin, Yu. B.; Finkel, M. I.; Antipov, S. V.; Voronov, B. M.; Smirnov, K. V.; Kaurova, N. S.; Drakinski, V. N.; Gol'tsman, G. N.
Title Superconducting hot-electron bolometer mixer for terahertz heterodyne receivers Type Journal Article
Year 2003 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal
Volume (down) 13 Issue 2 Pages 168-171
Keywords NbN HEB mixers
Abstract We present recent results showing the development of superconducting NbN hot-electron bolometer mixer for German receiver for astronomy at terahertz frequencies and terahertz limb sounder. The mixer is incorporated into a planar feed antenna, which has either logarithmic spiral or double-slot configuration, and backed on a silicon lens. The hybrid antenna had almost frequency independent and symmetric radiation pattern slightly broader than expected for a diffraction limited antenna. At 2.5 THz the best 2200 K double side-band receiver noise temperature was achieved across a 1 GHz intermediate frequency bandwidth centred at 1.5 GHz. For this operation regime, a receiver conversion efficiency of -17 dB was directly measured and the loss budget was evaluated. The mixer response was linear at load temperatures smaller than 400 K. Implementation of the MgO buffer layer on Si resulted in an increased 5.2 GHz gain bandwidth. The receiver was tested in the laboratory environment by measuring a methanol emission line at 2.5 THz.
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Notes Approved no
Call Number Serial 343
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Author Huebers, Heinz-Wilhelm; Pavlov, S.; Semenov, A.; Köhler, R.; Mahler, L.; Tredicucci, A.; Beere, H.; Ritchie, D.; Linfield, E.
Title Terahertz quantum cascade laser as local oscillator in a heterodyne receiver Type Journal Article
Year 2005 Publication Optics Express Abbreviated Journal
Volume (down) 13 Issue 15 Pages 5890-5896
Keywords QCL heterodyne, 6 mW at 2.5 THz, HEB mixer, terahertz
Abstract Terahertz quantum cascade lasers have been investigated with respect to their performance as a local oscillator in a heterodyne receiver. The beam profile has been measured and transformed in to a close to Gaussian profile resulting in a good matching between the field patterns of the quantum cascade laser and the antenna of a superconducting hot electron bolometric mixer. Noise temperature measurements with the hot electron bolometer and a 2.5 THz quantum cascade laser yielded the same result as with a gas laser as local oscillator.
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Notes Approved no
Call Number Serial 627
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Author Lang, P. T.; Knott, W. J.; Leipold, I.; Renk, K. F.; Semenov, A. D.; Gol'tsman, G. N.
Title Generation and detection of tunable ultrashort infrared and far-infrared radiation pulses of high intensity Type Journal Article
Year 1992 Publication Int. J. of Infrared and Millimeter Waves Abbreviated Journal Int. J. of Infrared and Millimeter Waves
Volume (down) 13 Issue 3 Pages 373-380
Keywords CO2 IR lasers, FIR
Abstract We report on generation and detection of intense pulsed radiation with frequency tunability in the infrared and far-infrared spectral regions. Infrared radiation is generated with a transversally electrically excited high pressure CO2 laser. A laser pulse of a total duration of about 300 ns consisted, due to self mode locking, of a series of single pulses, some with pulse durations of less than 450 ps and peak powers larger than 20 MW. Using these pulses for optical with durations less than 400 ps were obtained. For detection a new ultrafast superconducting detector was used.
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ISSN 0195-9271 ISBN Medium
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Notes Approved no
Call Number Serial 1671
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Author Schubert, J.; Semenov, A.; Gol'tsman, G.; Hübers, H.-W.; Schwaab, G.; Voronov, B.; Gershenzon, E.
Title Noise temperature of an NbN hot-electron bolometric mixer at frequencies from 0.7 THz to 5.2 THz Type Journal Article
Year 1999 Publication Supercond. Sci. Technol. Abbreviated Journal
Volume (down) 12 Issue 11 Pages 748-750
Keywords NbN HEB mixers
Abstract We report on noise temperature measurements of an NbN phonon-cooled hot-electron bolometric mixer in the terahertz frequency range. The devices were 3 nm thick films with in-plane dimensions 1.7 × 0.2 µm2 and 0.9 × 0.2 µm2 integrated in a complementary logarithmic-spiral antenna. Measurements were performed at seven frequencies ranging from 0.7 THz to 5.2 THz. The measured DSB noise temperatures are 1500 K (0.7 THz), 2200 K (1.4 THz), 2600 K (1.6 THz), 2900 K (2.5 THz), 4000 K (3.1 THz), 5600 K (4.3 THz) and 8800 K (5.2 THz).
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Notes Approved no
Call Number Serial 298
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