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Author Zhang, W.; Miao, W.; Li, S. L.; Zhou, K. M.; Shi, S. C.; Gao, J. R.; Goltsman, G. N. url  doi
openurl 
  Title Measurement of the spectral response of spiral-antenna coupled superconducting hot electron bolometers Type Journal Article
  Year 2013 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume 23 Issue 3 Pages 2300804-2300804  
  Keywords NbN HEB detector  
  Abstract Measured spectral response of spiral-antenna coupled superconducting hot electron bolometers (HEBs) often drops dramatically at frequencies that are still within the frequency range of interest (e.g., ~ 5 THz). This is inconsistent with the implied low receiver noise temperatures from the same measurements. To understand this discrepancy, we exhaustively test and calibrate the thermal sources used in Fourier transform spectrometer measurements. We first investigate the absolute emission spectrum of high-pressure Hg arc lamp, then measure the spectral response of two spiral-antenna coupled NbN HEBs with a Martin-Puplett interferometer as spectrometer and 77 K blackbody as broadband signal source. The measured absolute emission spectrum of Hg arc lamp is proportional to frequency, corresponding to an equivalent blackbody temperature of 4000 K at 1 THz, 1500 K at 3 THz, and 800 K at 5 THz, respectively. Measured spectral response of spiral-antenna coupled NbN HEBs, corrected for air absorption, is nearly flat in the frequency range of 0.5-4 THz, consistent with simulated coupling efficiency between HEB and spiral-antenna. These results explain the discrepancy, and prove that spiral-antenna coupled superconducting NbN HEBs work well in a wide frequency range. In addition, this calibration method and these results are broadly applicable to other quasi-optical THz receivers.  
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  Series Volume Series Issue Edition  
  ISSN 1051-8223 ISBN Medium  
  Area Expedition Conference  
  Notes (up) Approved no  
  Call Number Serial 1371  
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Author Shurakov, A.; Tong, C.-Y. E.; Blundell, R.; Kaurova, N.; Voronov, B.; Gol'tsman, G. url  doi
openurl 
  Title Microwave stabilization of a HEB mixer in a pulse-tube cryocooler Type Journal Article
  Year 2013 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume 23 Issue 3 Pages 1501504-1501504  
  Keywords NbN HEB mixers  
  Abstract We report the results of our study of the stability of an 800 GHz hot electron bolometer (HEB) mixer cooled with a pulse-tube cryocooler. Pulse-tube cryocoolers introduce temperature fluctuations as well as mechanical vibrations at a frequency of ~1 Hz, both of which can cause receiver gain fluctuations at that frequency. In our system, the motor of the cryocooler was separated from the cryostat to minimize mechanical vibrations, leaving thermal effects as the dominant source of the receiver gain fluctuations. We measured root mean square temperature variations of the 4 K stage of ~7 mK. The HEB mixer was pumped by a solid state local oscillator at 810 GHz. The root mean square current fluctuations at the low noise operating point (1.50 mV, 56.5 μA) were ~0.12 μA, and were predominantly due to thermal fluctuations. To stabilize the bias current, microwave radiation was injected to the HEB mixer. The injected power level was set by a proportional-integral-derivative controller, which completely compensates for the bias current oscillations induced by the pulse-tube cryocooler. Significant improvement in the Allan variance of the receiver output power was obtained, and an Allan time of 5 s was measured.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1051-8223 ISBN Medium  
  Area Expedition Conference  
  Notes (up) Approved no  
  Call Number Serial 1372  
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Author Lusche, R.; Semenov, A.; Il'in, K.; Korneeva, Y.; Trifonov, A.; Korneev, A.; Hubers, H.; Siegel, M.; Gol'tsman, G. url  doi
openurl 
  Title Effect of the wire width and magnetic field on the intrinsic detection efficiency of superconducting nanowire single-photon detectors Type Journal Article
  Year 2013 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume 23 Issue 3 Pages 2200205-2200205  
  Keywords SSPD, SNSPD  
  Abstract We present thorough measurements of the intrinsic detection efficiency in the wavelength range from 350 to 2500 nm for meander-type TaN and NbN superconducting nanowire single-photon detectors with different widths of the nanowire. The width varied from 70 nm to 130 nm. The open-beam configuration allowed us to accurately normalize measured spectra and to extract the intrinsic detection efficiency. For detectors from both materials the intrinsic detection efficiency at short wavelengths amounts at 100% and gradually decreases at wavelengths larger than the specific cut-off wavelengths, which decreases with the width of the nanowire. Furthermore, we show that applying weak magnetic fields perpendicular to the meander plane decreases the smallest detectable photon flux.  
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  ISSN 1051-8223 ISBN Medium  
  Area Expedition Conference  
  Notes (up) Approved no  
  Call Number Serial 1376  
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Author Korneev, A. A.; Divochiy, A. V.; Vakhtomin, Yu. B.; Korneeva, Yu. P.; Larionov, P. A.; Manova, N. N.; Florya, I. N.; Trifonov, A. V.; Voronov, B. M.; Smirnov, K. V.; Semenov, A. V.; Chulkova, G. M.; Goltsman, G. N. url  openurl
  Title IR single-photon receiver based on ultrathin NbN superconducting film Type Journal Article
  Year 2013 Publication Rus. J. Radio Electron. Abbreviated Journal Rus. J. Radio Electron.  
  Volume Issue 5 Pages  
  Keywords SSPD, SNSPD  
  Abstract We present our recent results in research and development of superconducting single-photon detector (SSPD). We achieved the following performance improvement: first, we developed and characterized SSPD integrated in optical cavity and enabling its illumination from the face side, not through the substrate, second, we improved the quantum efficiency of the SSPD at around 3 μm wavelength by reduction of the strip width to 40 nm, and, finally, we improved the detection efficiency of the SSPD-based single-photon receiver system up to 20% at 1550 nm and extended its wavelength range beyond 1800 nm by the usage of the fluoride ZBLAN fibres.  
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  Language Russian Summary Language Original Title  
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  Notes (up) 8 pages Approved no  
  Call Number RPLAB @ sasha @ korneevir Serial 1043  
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Author Beck, M.; Rousseau, I.; Klammer, M.; Leiderer, P.; Mittendorff, M.; Winnerl, S.; Helm, M.; Gol'tsman, G.N.; Demsar, J. url  doi
openurl 
  Title Transient increase of the energy gap of superconducting NbN thin films excited by resonant narrow-band terahertz pulses Type Journal Article
  Year 2013 Publication Phys. Rev. Lett. Abbreviated Journal Phys. Rev. Lett.  
  Volume 110 Issue 26 Pages 267003 (1 to 5)  
  Keywords NbN thin films, energy gap  
  Abstract Observations of radiation-enhanced superconductivity have thus far been limited to a few type-I superconductors (Al, Sn) excited at frequencies between the inelastic scattering rate and the superconducting gap frequency 2Delta/h. Utilizing intense, narrow-band, picosecond, terahertz pulses, tuned to just below and above 2Delta/h of a BCS superconductor NbN, we demonstrate that the superconducting gap can be transiently increased also in a type-II dirty-limit superconductor. The effect is particularly pronounced at higher temperatures and is attributed to radiation induced nonthermal electron distribution persisting on a 100 ps time scale.  
  Address Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457, Germany  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0031-9007 ISBN Medium  
  Area Expedition Conference  
  Notes (up) PMID:23848912 Approved no  
  Call Number Serial 1370  
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