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Author Sidorova, M. V.; Kozorezov, A. G.; Semenov, A. V.; Korneev, A. A.; Chulkova, G. M.; Korneeva, Y. P.; Mikhailov, M. Y.; Devizenko, A. Y.; Goltsman, G. N. url  openurl
  Title Non-bolometric bottleneck in electron-phonon relaxation in ultra-thin WSi film Type Miscellaneous
  Year 2018 Publication arXiv Abbreviated Journal  
  Volume Issue Pages  
  Keywords WSi films, diffusion constant, SSPD, SNSPD  
  Abstract We developed the model of the internal phonon bottleneck to describe the energy exchange between the acoustically soft ultrathin metal film and acoustically rigid substrate. Discriminating phonons in the film into two groups, escaping and nonescaping, we show that electrons and nonescaping phonons may form a unified subsystem, which is cooled down only due to interactions with escaping phonons, either due to direct phonon conversion or indirect sequential interaction with an electronic system. Using an amplitude-modulated absorption of the sub-THz radiation technique, we studied electron-phonon relaxation in ultrathin disordered films of tungsten silicide. We found an experimental proof of the internal phonon bottleneck. The experiment and simulation based on the proposed model agree well, resulting in tau{e-ph} = 140-190 ps at TC = 3.4 K, supporting the results of earlier measurements by independent techniques.  
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  Notes Duplicated as 1305 Approved no  
  Call Number Serial 1341  
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Author Sidorova, M.; Semenov, A.; Korneev, A.; Chulkova, G.; Korneeva, Y.; Mikhailov, M.; Devizenko, A.; Kozorezov, A.; Goltsman, G. url  openurl
  Title Electron-phonon relaxation time in ultrathin tungsten silicon film Type Miscellaneous
  Year 2018 Publication arXiv Abbreviated Journal  
  Volume Issue Pages  
  Keywords WSi film  
  Abstract Using amplitude-modulated absorption of sub-THz radiation (AMAR) method, we studied electron-phonon relaxation in thin disordered films of tungsten silicide. We found a response time ~ 800 ps at critical temperature Tc = 3.4 K, which scales as minus 3 in the temperature range from 1.8 to 3.4 K. We discuss mechanisms, which can result in a strong phonon bottle-neck effect in a few nanometers thick film and yield a substantial difference between the measured time, characterizing response at modulation frequency, and the inelastic electron-phonon relaxation time. We estimate the electron-phonon relaxation time to be in the range ~ 100-200 ps at 3.4 K.  
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  Notes Duplicated as 1341 Approved no  
  Call Number Serial 1340  
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Author Nikoghosyan, A. S.; Martirosyan, R. M.; Hakhoumian, A. A.; Makaryan, A. H.; Tadevosyan, V. R.; Goltsman, G. N.; Antipov, S. V. url  openurl
  Title Effect of absorption on the efficiency of THz radiation generation in a nonlinear crystal placed into a waveguide Type Journal Article
  Year 2018 Publication Armenian J. Phys. Abbreviated Journal Armenian J. Phys.  
  Volume 11 Issue 4 Pages 257-262  
  Keywords THz, waveguide, nonlinear crystal  
  Abstract The effect of THz radiation absorption on the efficiency of generation of coherent THz radiation in a nonlinear optical crystal placed into a metal rectangular waveguide is studied. The efficiency of the nonlinear conversion of optical laser radiation to the THz band is also a function of the phase-matching (PM) condition inside the nonlinear crystal. The method of partial filling of a metal waveguide with a nonlinear optical crystal is used to ensure phase matching. Phase matching was obtained by the proper choice of the thickness of the nonlinear crystal, namely the degree of partial filling of the waveguide. We have studied the THz radiation attenuation caused by the losses in both the metal walls of the waveguide and in the crystal, taking into account the dimension of the cross section of the waveguide, the degree of partial filling and its dielectric constant.  
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  ISSN 1829-1171 ISBN Medium  
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  Notes Approved no  
  Call Number Serial 1291  
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Author Zolotov, P.; Divochiy, A.; Vakhtomin, Y.; Moshkova, M.; Morozov, P.; Seleznev, V.; Smirnov, K. url  doi
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  Title Photon-number-resolving SSPDs with system detection efficiency over 50% at telecom range Type Conference Article
  Year 2018 Publication Proc. AIP Conf. Abbreviated Journal  
  Volume 1936 Issue 1 Pages 020019  
  Keywords NbN PNR SSPD, SNSPD  
  Abstract We used technology of making high-efficiency superconducting single-photon detectors as a basis for improvement of photon-number-resolving devices. By adding optical cavity and using an improved NbN superconducting film, we enhanced previously reported system detection efficiency at telecom range for such detectors. Our results show that implementation of optical cavity helps to develop four-section device with quantum efficiency over 50% at 1.55 µm. Performed experimental studies of detecting multi-photon optical pulses showed irregularities over defining multi-photon through single-photon quantum efficiency.  
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  Call Number doi:10.1063/1.5025457 Serial 1231  
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Author Baeva, E.; Sidorova, M.; Korneev, A.; Goltsman, G. url  doi
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  Title Precise measurement of the thermal conductivity of superconductor Type Conference Article
  Year 2018 Publication Proc. AIP Conf. Abbreviated Journal Proc. AIP Conf.  
  Volume 1936 Issue 1 Pages 020003 (1 to 4)  
  Keywords NbN SSPD, SNSPD  
  Abstract Measuring the thermal properties such as the heat capacity provide information about intrinsic mechanisms operated inside. In general, the ratio between electron and phonon specific heat Ce/Cp shows how the absorbed energy shared between electron and phonon subsystems. In this work we make estimations for amplitude-modulated absorption of THz radiation technique for investigation of the ratio Ce/Cp in superconducting Niobium Nitride (NbN) at T = Tc. Our results indicates that experimentally the frequency of modulation has to be extra large to extract the quantity. We perform a new technique allowed to work at low frequency with accurately measurement of absorbed power.  
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  Notes Approved no  
  Call Number doi:10.1063/1.5025441 Serial 1311  
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