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Author Yagoubov, P.; Kroug, M.; Merkel, H.; Kollberg, E.; Gol'tsman, G.; Svechnikov, S.; Gershenzon, E. url  doi
openurl 
  Title Noise temperature and local oscillator power requirement of NbN phonon-cooled hot electron bolometric mixers at terahertz frequencies Type Journal Article
  Year 1998 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.  
  Volume (up) 73 Issue 19 Pages 2814-2816  
  Keywords NbN HEB mixers, noise temperature, local oscillator power  
  Abstract In this letter, the noise performance of NbN-based phonon-cooled hot electron bolometric quasioptical mixers is investigated in the 0.55–1.1 THz frequency range. The best results of the double-sideband <cd><2018>DSB<cd><2019> noise temperature are: 500 K at 640 GHz, 600 K at 750 GHz, 850 K at 910 GHz, and 1250 K at 1.1 THz. The water vapor in the signal path causes significant contribution to the measured receiver noise temperature around 1.1 THz. The devices are made from 3-nm-thick NbN film on high-resistivity Si and integrated with a planar spiral antenna on the same substrate. The in-plane dimensions of the bolometer strip are typically 0.2Ï«2 um. The amount of local oscillator power absorbed in the bolometer is less than 100 nW.  
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  Notes Approved no  
  Call Number Serial 911  
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Author Gousev, Yu. P.; Gol'tsman, G. N.; Semenov, A. D.; Gershenzon, E. M.; Nebosis, R. S.; Heusinger, M. A.; Renk, K. F. doi  openurl
  Title Broadband ultrafast superconducting NbN detector for electromagnetic radiation Type Journal Article
  Year 1994 Publication J. Appl. Phys. Abbreviated Journal J. Appl. Phys.  
  Volume (up) 75 Issue 7 Pages 3695-3697  
  Keywords NbN HEB  
  Abstract An ultrafast detector that is sensitive to radiation in a broad spectral range from submillimeter waves to visible light is reported. It consists of a structured NbN thin film cooled to a temperature below Tc (∼11 K). Using 20 ps pulses of a GaAs laser, we observed signal pulses with both rise and decay time of about 50 ps. From the analysis of a mixing experiment with submillimeter radiation we estimate an intrinsic response time of the detector of ∼12 ps. The sensitivity was found to be similar for the near‐infrared and submillimeter radiation. Broadband sensitivity and short response time are attributed to a quasiparticle heating effect.  
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  Notes Approved no  
  Call Number Serial 252  
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Author Gershenzon, E. M.; Gol'tsman, G. N.; Potapov, V. D.; Sergeev, A. V. url  doi
openurl 
  Title Restriction of microwave enhancement of superconductivity in impure superconductors due to electron-electron interaction Type Journal Article
  Year 1990 Publication Solid State Communications Abbreviated Journal Solid State Communications  
  Volume (up) 75 Issue 8 Pages 639-641  
  Keywords impure superconductors  
  Abstract Transition from microwave enhancement of supercurrent to superconductivity suppression is investigated in impure superconductors. It is demonstrated that the frequency range of the enhancement effect narrows with the decrease of the electron mean free path, l, and at l ⩽ 1 nm electron heating is observed in the whole frequency range. Dependences of frequency boundaries on l are explained by taking into account strong electron-electron interaction in impure metals.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0038-1098 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1687  
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Author Il'in, K. S.; Lindgren, M.; Currie, M. A.; Semenov, D.; Gol'tsman, G. N.; Sobolewski, Roman; Cherednichenko, S. I.; Gershenzon, E. M. url  doi
openurl 
  Title Picosecond hot-electron energy relaxation in NbN superconducting photodetectors Type Journal Article
  Year 2000 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.  
  Volume (up) 76 Issue 19 Pages 2752-2754  
  Keywords NbN HEB detectors, two-temperature model, IF bandwidth  
  Abstract We report time-resolved characterization of superconducting NbN hot-electron photodetectors using an electro-optic sampling method. Our samples were patterned into micron-size microbridges from 3.5-nm-thick NbN films deposited on sapphire substrates. The devices were illuminated with 100 fs optical pulses, and the photoresponse was measured in the ambient temperature range between 2.15 and 10.6 K (superconducting temperature transition TC). The experimental data agreed very well with the nonequilibrium hot-electron, two-temperature model. The quasiparticle thermalization time was ambient temperature independent and was measured to be 6.5 ps. The inelastic electron–phonon scattering time Ï„e–ph tended to decrease with the temperature increase, although its change remained within the experimental error, while the phonon escape time Ï„es decreased almost by a factor of two when the sample was put in direct contact with superfluid helium. Specifically, Ï„e–ph and Ï„es, fitted by the two-temperature model, were equal to 11.6 and 21 ps at 2.15 K, and 10(±2) and 38 ps at 10.5 K, respectively. The obtained value of Ï„e–ph shows that the maximum intermediate frequency bandwidth of NbN hot-electron phonon-cooled mixers operating at TC can reach 16(+4/–3) GHz if one eliminates the bolometric phonon-heating effect.  
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  ISSN 0003-6951 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 856  
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Author Gershenzon, E. M.; Gol'tsman, G. N.; Semenov, A. D.; Sergeev, A. V. url  doi
openurl 
  Title Mechanism of picosecond response of granular YBaCuO films to electromagnetic radiation Type Journal Article
  Year 1990 Publication Solid State Communications Abbreviated Journal Solid State Communications  
  Volume (up) 76 Issue 4 Pages 493-497  
  Keywords YBCO HTS detectors  
  Abstract The ultrafast mechanisms of radiation detection in granular YBaCuO films are studied in the wide wavelength range from millimeter to near infrared. With the rise of radiation frequency the Josephson detection at the grain boundary weak links is replaced by electron heating into the grains. This change occurs in the submillimeter wavelength range. Electron-phonon relaxation time τeph is determined by direct measurements and analyses quasistationary electron heating. Temperature dependence of τeph at T ≤ 40 K was found to be τeph ∼ T−1. The results show that detectors with the response time of few picoseconds at nitrogen temperature are attainable.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0038-1098 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1685  
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