Semenov AD, Heusinger MA, Renk KF, Menschikov E, Sergeev AV, Elant'ev AI, et al. Influence of phonon trapping on the performance of NbN kinetic inductance detectors. IEEE Trans Appl Supercond. 1997;7(2):3083–6.
Abstract: Voltage and microwave photoresponse of NbN thin films to modulated and pulsed optical radiation reveals, far below the superconducting transition, a response time consistent with the lifetime of nonequilibrium quasiparticles. We show that even in 5 nm thick films at 4.2 K the phonon trapping is significant resulting in a quasiparticle lifetime of a few nanoseconds that is an order of magnitude larger than the recombination time. Values and temperature dependence of the quasiparticle lifetime obey the Bardeen-Cooper-Schrieffer theory and are in quantitative agreement with the electron-phonon relaxation rate determined from the resistive response near the superconducting transition. We discuss a positive effect of the phonon trapping on the performance of kinetic inductance detectors.
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Nebosis RS, Heusinger MA, Schatz W, Renk KF, Gol’tsman GN, Karasik BS, et al. Ultrafast photoresponse of a structured YBa2Cu3O7-δ thin film to ultrashort FIR laser pulses. IEEE Trans Appl Supercond. 1993;3(1):2160–2.
Abstract: The authors have investigated the photoinduced voltage response of a current-carrying structured YBa2Cu3O7-δ thin film to ultrashort far-infrared (FIR) laser pulses in the frequency range from 0.7 THz to 7 THz. The detector has shown an almost constant sensitivity of 1 mV/W and a noise equivalent power of less than 5*10/sup -7/ W/ square root Hz. The temperature dependence of the decay time of the detector signal was studied for temperatures around the transition temperature of the film ( approximately 80 K). For a detector temperature where dR/dT had its maximum, the authors observed bolometric signals with decay times of about 2 ns, and for lower temperatures they observed nonbolometric signals with decay times of approximately 120 ps; the duration of the nonbolometric signals was limited by the time resolution of the electronic registration equipment.
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Semenov AD, Sergeev AV, Kouminov P, Goghidze IG, Heusinger MA, Nebosis RS, et al. Transparency of YBCO film/substrate interfaces for thermal phonons determined by photoresponse measurements. In: Freyhardt HC, editor. Proc. 1st European Conf. on Appl. Supercond. Vol 2.; 1993. p. 1443–6.
Abstract: Direct measurements of the thermal boundary resistance were performed by means of the stationary method. In this approach the temperature of an electrically heated film is controlled by its dc resistance while an additional film on the same substrate is used as a thermometer monitoring substrate temperature. The temperature field in the substrate is then calculated to deduce the Kapitza temperature step at the interface between the heated strip and the substrate. The main statement of all afore-said papers is that experimental values of the thermal boundary resistance are too large to be explained by the acoustic mismatch model. In this paper we investigate transparency of YBaCuO film/substrate interfaces for thermal phonons by means of photoresponse measurements. We show that our data are in reasonable agreement with the acoustic mismatch theory.
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Semenov AD, Gol’tsman GN, Gogidze IG, Sergeev AV, Gershenzon EM, Lang PT, et al. Subnanosecond photoresponse of a YBaCuO thin film to infrared and visible radiation by quasiparticle induced suppression of superconductivity. Appl Phys Lett. 1992;60(7):903–5.
Abstract: We observed subnanosecond photoresponse of a structured superconducting YBa2Cu3O7−δ thin film to infrared and visible radiation. We measured the voltage response of a current biased film (thickness 700 Å) in a resistive state to radiation pulses. From our results we conclude a response time of about 90 ps and a responsivity of about 4×1010 Ω/J. We attribute the response to Cooper pair breaking and suppression of the superconducting energy gap induced by nonequilibrium quasiparticles.
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Nebosis RS, Semenov AD, Gousev YP, Renk KF. Rigorous analysis of a superconducting hot-electron bolometer mixer: theory and comparision with experiment. In: Proc. 7th Int. Symp. Space Terahertz Technol. Charlottesville, Virginia, USA; 1996. p. 601–13.
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