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Author Ryabchun, S. A.; Tretyakov, I. V.; Pentin, I. V.; Kaurova, N. S.; Seleznev, V. A.; Voronov, B. M.; Finkel, M. I.; Maslennikov, S. N.; Gol'tsman, G. N. doi  openurl
  Title Low-noise wide-band hot-electron bolometer mixer based on an NbN film Type Journal Article
  Year 2009 Publication Radiophys. Quant. Electron. Abbreviated Journal  
  Volume 52 Issue 8 Pages 576-582  
  Keywords HEB mixer, in-situ contacts, noise temperature, conversion gain bandwidth, diffusion cooling channel  
  Abstract We develop and study a hot-electron bolometer mixer made of a two-layer NbN–Au film in situ deposited on a silicon substrate. The double-sideband noise temperature of the mixer is 750 K at a frequency of 2.5 THz. The conversion efficiency measurements show that at the superconducting transition temperature, the intermediate-frequency bandwidth amounts to about 6.5 GHz for a mixer 0.112 μm long. These record-breaking characteristics are attributed to the improved contacts between a sensitive element and a helical antenna and are reached due to using the in situ deposition of NbN and Au layers at certain stages of the process.  
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  Notes Approved no  
  Call Number Serial 599  
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Author Beck, M.; Klammer, M.; Lang, S.; Leiderer, P.; Kabanov, V. V.; Gol'tsman, G. N.; Demsar, J. doi  openurl
  Title Energy-gap dynamics of superconducting NbN thin films studied by time-resolved terahertz spectroscopy Type Journal Article
  Year 2011 Publication Phys. Rev. Lett. Abbreviated Journal Phys. Rev. Lett.  
  Volume 107 Issue 17 Pages 4  
  Keywords NbN thin film, energy gap dynamics  
  Abstract Using time-domain terahertz spectroscopy we performed direct studies of the photoinduced suppression and recovery of the superconducting gap in a conventional BCS superconductor NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the bare quasiparticle recombination rate, the Cooper pair-breaking rate and the electron-phonon coupling constant, λ=1.1±0.1, which is in excellent agreement with theoretical estimates.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 641  
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Author Manova, N. N.; Korneeva, Yu. P.; Korneev, A. A.; Slysz, W.; Voronov, B. M.; Gol'tsman, G. N. url  doi
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  Title Superconducting NbN single-photon detector integrated with quarter-wave resonator Type Journal Article
  Year 2011 Publication Tech. Phys. Lett. Abbreviated Journal Tech. Phys. Lett.  
  Volume 37 Issue 5 Pages 469-471  
  Keywords SSPD, SNSPD  
  Abstract The spectral dependence of the quantum efficiency of superconducting NbN single-photon detectors integrated with quarter-wave resonators based on Si3N4, SiO2, and SiO layers has been studied.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 664  
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Author Ozhegov, R. V.; Gorshkov, K. N.; Gol'tsman, G. N.; Kinev, N. V.; Koshelets, V. P. doi  openurl
  Title The stability of a terahertz receiver based on a superconducting integrated receiver Type Journal Article
  Year 2011 Publication Supercond. Sci. Technol. Abbreviated Journal Supercond. Sci. Technol.  
  Volume 24 Issue 3 Pages 035003  
  Keywords SIS mixer, SIR, stability  
  Abstract We present the results of stability testing of a terahertz radiometer based on a superconducting receiver with a SIS tunnel junction as the mixer and a flux-flow oscillator as the local oscillator. In the continuum mode, the receiver with a noise temperature of 95 K at 510 GHz measured over the intermediate frequency (IF) passband of 4-8 GHz offered a noise equivalent temperature difference of 10 ± 1 mK at an integration time of 1 s. We offer a method to significantly increase the integration time without the use of complex measurement equipment. The receiver observed a strong signal over a final detection bandwidth of 4 GHz and offered an Allan time of 5 s.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 705  
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Author Lobanov, Y.; Tong, E.; Blundell, R.; Hedden, A.; Voronov, B.; Gol'tsman, G. doi  openurl
  Title Large-signal frequency response of an HEB mixer: from 300 MHz to terahertz Type Journal Article
  Year 2011 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal  
  Volume 21 Issue 3 Pages 628-631  
  Keywords waveguide NbN HEB mixers  
  Abstract We present a study of the large signal frequency response of an HEB mixer over a wide frequency range. In our experiments, we have subjected the HEB mixer to incident electromagnetic radiation from 0.3 GHz to 1 THz. The mixer element is an NbN film deposited on crystalline quartz. The mixer chip is mounted in a waveguide cavity, coupled to free space with a diagonal horn. At microwave frequencies, electromagnetic radiation is applied through the coaxial bias port of the mixer block. At higher frequencies the input signal passes via the diagonal horn feed. At each frequency, the incident power is varied and a family of I-V curves is recorded. From the curves we identify 3 distinct regimes of operation of the mixer separated by the phonon relaxation frequency and the superconducting energy gap frequency observed at about 3 GHz and 660 GHz respectively. In this paper, we will present observed curves and discuss the results of our experiment.  
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  Call Number RPLAB @ gujma @ Serial 719  
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Author Lobanov, Y.V.; Tong, C.-Y.E.; Hedden, A.S.; Blundell, R.; Voronov, B.M.; Gol'tsman, G.N. doi  openurl
  Title Direct measurement of the gain and noise bandwidths of HEB mixers Type Journal Article
  Year 2011 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume 21 Issue 3 Pages 645-648  
  Keywords waveguide NbN HEB mixers  
  Abstract The intermediate frequency (IF) bandwidth of a hot electron bolometer (HEB) mixer is an important parameter of the mixer, in that it helps to determine its suitability for a given application. With the availability of wideband low noise amplifiers, it is simple to measure the performance of an HEB mixer over a wide range of IF at a fixed LO frequency using the standard Y-factor method. This in-situ method allows us to measure both the gain and noise bandwidths simultaneously. We have also measured mixer output impedance with a vector network analyser. Intrinsic time constant has been extracted from the impedance data and compared to the mixer's bandwidths determined from receiver Y-factor measurement.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 720  
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Author Seleznev, V. A.; Tarkhov, M. A.; Voronov, B. M.; Milostnaya, I. I.; Lyakhno, V. Yu; Garbuz, A. S.; Mikhailov, M. Yu; Zhigalina, O. M.; Gol'tsman, G. N. doi  openurl
  Title Deposition and characterization of few-nanometers-thick superconducting Mo-Re films Type Journal Article
  Year 2008 Publication Supercond. Sci. Technol. Abbreviated Journal Supercond. Sci. Technol.  
  Volume 21 Issue 11 Pages 115006 (1 to 6)  
  Keywords  
  Abstract We report on the fabrication and investigation of few-nanometers-thick superconducting molybdenum-rhenium (Mo-Re) films intended for use in nanowire single-photon superconducting detectors (SSPDs). Mo-Re films were deposited on sapphire substrates by DC magnetron sputtering of an Mo(60)-Re(40) alloy target in an atmosphere of argon. The films 2-10 nm thick had critical temperatures (Tc) from 5.6 to 9.7 K. HRTEM (high-resolution transmission electron microscopy) analysis showed that the films had a homogeneous structure. XPS (x-ray photoelectron spectroscopy) analysis showed the Mo to Re atom ratio to be 0.575/0.425, oxygen concentration to be 10%, and concentration of other elements to be 1%.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 723  
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Author Lobanov, Y.; Tong, C.; Blundell, R.; Gol'tsman, G. url  openurl
  Title A study of direct detection effect on the linearity of hot electron bolometer mixers Type Conference Article
  Year 2009 Publication Proc. 20th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 20th ISSTT  
  Volume Issue Pages 282-287  
  Keywords HEB mixer, direct detection effect  
  Abstract We have performed a study of how direct detection affects the linearity and hence the calibration of an HEB mixer. Two types of waveguide HEB devices have been used: a 0.8 THz HEB mixer and a 1.0 THz HEB mixer which is ~5 times smaller than the former. Two independent experimental approaches were used. In the ΔG/G method, the conversion gain of the HEB mixer is first measured as a function of the bias current for a number of bias voltages. At each bias setting, we carefully measure the change in the operating current when the input loads are switched. From the measured data, we can derive the expected difference in gain between the hot and cold loads. In the second method (injection method [1]), the linearity of the HEB mixer is independently measured by injecting a modulated signal for different input load temperatures. The results of both approaches confirm that there is gain compression in the operation of HEB mixers. Based on the results of our measurements, we discuss the impact of direct detection effects on the operation of HEB mixers.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 724  
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Author Lobanov, Y. V.; Tong, Cheuk-Yu E.; Hedden, A. S.; Blundell, R.; Gol'tsman, G. N. openurl 
  Title Microwave-assisted슠measurement슠of the슠frequency슠response슠of슠terahertz슠HEB슠mixers슠with a슠fourier슠transform슠spectrometer Type Conference Article
  Year 2010 Publication 21st International Symposium on Space Terahertz Technology Abbreviated Journal 21st ISSTT  
  Volume Issue Pages 420-423  
  Keywords HEB mixer  
  Abstract We describe a novel method of operation of the HEB direct detector for use with a Fourier Transform Spectrometer. Instead of elevating the bath temperature, we have measured the RF response of waveguide HEB mixers by applying microwave radiation to select appropriate bias conditions. In our experiment, a microwave signal is injected into the HEB mixer via its IF port. By choosing an appropriate injection level, the device can be operated close to the desired operating point. Furthermore, we have shown that both thermal biasing and microwave injection can reproduce the same spectral response of the HEB mixer. However, with the use of microwave injection, there is no need to wait for the mixer to reach thermal equilibrium, so characterisation can be done in less time. Also, the liquid helium consumption for our wet cryostat is also reduced. We have demonstrated that the signalto-noise ratio of the FTS measurements can be improved with microwave injection.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 725  
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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 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 Bell, M.; Sergeev, A.; Mitin, V.; Bird, J.; Verevkin, A.; Gol'tsman, G. openurl 
  Title One-dimensional resistive states in quasi-two-dimensional superconductors Type Journal Article
  Year 2007 Publication arXiv:0709.0709v1 [cond-mat.supr-con] Abbreviated Journal  
  Volume Issue Pages 1-11  
  Keywords  
  Abstract We investigate competition between one- and two-dimensional topological excitations – phase slips and vortices – in formation of resistive states in quasi-two-dimensional superconductors in a wide temperature range below the mean-field transition temperature T(C0). The widths w = 100 nm of our ultrathin NbN samples is substantially larger than the Ginzburg-Landau coherence length ξ = 4nm and the fluctuation resistivity above T(C0) has a two-dimensional character. However, our data shows that the resistivity below T(C0) is produced by one-dimensional excitations, – thermally activated phase slip strips (PSSs) overlapping the sample cross-section. We also determine the scaling phase diagram, which shows that even in wider samples the PSS contribution dominates over vortices in a substantial region of current/temperature variations. Measuring the resistivity within seven orders of magnitude, we find that the quantum phase slips can only be essential below this level.  
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  Notes Approved no  
  Call Number RPLAB @ atomics90 @ Serial 948  
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Author Lobanov, Y.; Shcherbatenko, M.; Finkel, M.; Maslennikov, S.; Semenov, A.; Voronov, B. M.; Rodin, A. V.; Klapwijk, T. M.; Gol'tsman, G. N. doi  openurl
  Title NbN hot-electron-bolometer mixer for operation in the near-IR frequency range Type Journal Article
  Year 2015 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume 25 Issue 3 Pages 2300704 (1 to 4)  
  Keywords HEB mixer, IR, optical antenna  
  Abstract Traditionally, hot-electron-bolometer (HEB) mixers are employed for THz and “super-THz” heterodyne detection. To explore the near-IR spectral range, we propose a fiber-coupled NbN film based HEB mixer. To enhance the incident-light absorption, a quasi-antenna consisting of a set of parallel stripes of gold is used. To study the antenna effect on the mixer performance, we have experimentally studied a set of devices with different size of the Au stripe and spacing between the neighboring stripes. With use of the well-known isotherm technique we have estimated the absorption efficiency of the mixer, and the maximum efficiency has been observed for devices with the smallest pitch of the alternating NbN and NbN-Au stripes. Also, a proper alignment of the incident Eâƒ<2014>-field with respect to the stripes allows us to improve the coupling further. Studying IV-characteristics of the mixer under differently-aligned Eâƒ<2014>-field of the incident radiation, we have noticed a difference in their shape. This observation suggests that a difference exists in the way the two waves with orthogonal polarizations parallel and perpendicular Eâƒ<2014>-field to the stripes heat the electrons in the HEB mixer. The latter results in a variation in the electron temperature distribution over the HEB device irradiated by the two waves.  
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  Notes Approved no  
  Call Number Serial 952  
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Author Verevkin, A.; Zhang, J.; Slysz, W.; Sobolewski, Roman; Lipatov, A.; Okunev, O.; Chulkova, G.; Korneev, A.; Smimov, K.; Gol'tsman, G. N. url  openurl
  Title Spectral sensitivity and temporal resolution of NbN superconducting single-photon detectors Type Conference Article
  Year 2002 Publication Proc. 13th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 13th Int. Symp. Space Terahertz Technol.  
  Volume Issue Pages 105-111  
  Keywords NbN SSPD, SNSPD  
  Abstract We report our studies on spectral sensitivity and time resolution of superconducting NbN thin film single-photon detectors (SPDs). Our SPDs exhibit an everimentally measured detection efficiencies (DE) from — 0.2% at 2=1550 nm up to —3% at lambda=405 nm wavelength for 10-nm film thickness devices and up to 3.5% at lambda=1550 nm for 3.5-nm film thickness devices. Spectral dependences of detection efficiency (DE) at 2=0.4 —3.0 pm range are presented. With variable optical delay setup, it is shown that NbN SPD potentially can resolve optical pulses with the repetition rate up to 10 GHz at least. The observed full width at the half maximum (FWHM) of the signal pulse is about 150-180 ps, limited by read-out electronics. The jitter of NbN SPD is measured to be —35 ps at optimum biasing.  
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  Notes Approved no  
  Call Number Serial 1528  
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Author Dzardanov, A.; Ekstrom, H.; Gershenzon, E.; Gol'tsman, G.; Jacobsson, S.; Karasik, B.; Kollberg, E.; Okunev, O.; Voronov, B.; Yngvesson, S. doi  openurl
  Title Hot-electron superconducting mixers for 20-500 GHz operation Type Conference Article
  Year 1994 Publication Proc. Int. Conf. on Millimeter and Submillimeter Waves and Appl. Abbreviated Journal  
  Volume 2250 Issue 4D Pages 276-278  
  Keywords  
  Abstract Bolometdcmucers based on Nb and NbN superconducting thin films in the resistive state have been prepared for 20, 100 GHz and 350-500 GHz operation. The mixing mechanism is presumably of electron heating origin. Our measurements indicate that a conversion loss of about 6-8 dB can rather easily be achieved, and that the noise is reasonably low. The requirements on the operation mode and on the film parameters in order to obtain small conversion losses or even gain are discussed. For NbN films the availability of nearly 1 GHz IF bandwidth is experimentally demonstrated. NbN hot-electron mucers combined with slot-line tapered antenna on Si membrane or with double-dipole antenna on SiO^ substrate have been fabricated. The devices we study are considered to be very promising for use in heterodyne receivers from microwaves to terahertz frequencies.  
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  Notes Approved no  
  Call Number RPLAB @ phisix @ Serial 981  
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Author Gershenzon, E. M.; Gol'tsman, G. N.; Multanovskii, V. V.; Ptitsina, N. G. url  openurl
  Title Kinetics of electron and hole binding into excitons in germanium Type Journal Article
  Year 1983 Publication Sov. Phys. JETP Abbreviated Journal Sov. Phys. JETP  
  Volume 57 Issue 2 Pages 369-376  
  Keywords Ge, electron and hole binding  
  Abstract The kinetics of binding of free carriers'into excitons under stationary and nonstationary conditions is studied by investigating the submillimeter photoconductivity of Ge in a wide range of temperatures and of excitation levels. It is shown that the absolute values and the temperature dependence of the binding cross section (o- T-'.' ) can be satisfactorily described by the cascade recombination theory. The value of o and its temperature dependence differ significantly from the cross sections, measured in the same manner, for capture by attracting small impurities. Under nonstationary conditions, just as in the case of recombination with shallow impurities, a signifi- cant role is played by the sticking of the carriers in highly excited states.  
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  Notes Approved no  
  Call Number Serial 1711  
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