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Gol'tsman G, Korneev A, Minaeva O, Antipov A, Divochiy A, Kaurova N, et al. Middle-infrared to visible-light ultrafast superconducting single-photon detector. In: Proc. ASC. Seattle; 2006.
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Kitaygorsky J, Komissarov I, Jukna A, Minaeva O, Kaurova N, Divochiy A, et al. Fluctuations in two-dimensional superconducting NbN nanobridges and nanostructures meanders [abstract]. In: Proc. APS March Meeting. Vol 52.; 2007. L9.00013.
Abstract: We have observed fluctuations, manifested as sub-nanosecond to nanosecond transient, millivolt-amplitude voltage pulses, generated in two-dimensional NbN nanobridges, as well as in extended superconducting meander nanostructures, designed for single photon counting. Both nanobridges and nano-stripe meanders were biased at currents close to the critical current and measured in a range of temperatures from 1.5 to 8 K. During the tests, the devices were blocked from all incoming radiation by a metallic enclosure and shielded from any external magnetic fields. We attribute the observed spontaneous voltage pulses to the Kosterlitz-Thouless-type fluctuations, where the high enough applied bias current reduces the binding energy of vortex-antivortex pairs and, subsequently, thermal fluctuations break them apart causing the order parameter to momentarily reduce to zero, which in turn causes a transient voltage pulse. The duration of the voltage pulses depended on the device geometry (with the high-kinetic inductance meander structures having longer, nanosecond, pulses) while their rate was directly related to the biasing current as well as temperature.
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Gerecht E, Musante CF, Jian H, Yngvesson KS, Dickinson J, Waldman J, et al. Measured results for NbN phonon-cooled hot electron bolometric mixers at 0.6-0.75 THz, 1.56 THz, and 2.5 THz. In: Proc. 9th Int. Symp. Space Terahertz Technol.; 1998. p. 105–14.
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Svechnikov S, Verevkin A, Voronov B, Menschikov E, Gershenzon E, Gol'tsman G. Quasioptical phonon-cooled NbN hot electron bolometer mixers at 0.5-1.1 THz. In: Proc. 9th Int. Symp. Space Terahertz Technol.; 1998. p. 45–51.
Abstract: The noise performance of a receiver incorporating spiral antenna coupled NbN phonon-cooled superconducting hot electron bolometric mixer is measured from 450 GHz to 1200 GHz. The mixer element is thin (thickness nm) NbN 1.5 pm wide and 0.2 i.um long film fabricated by lift-off e-beam lithography on high-resistive silicon substrate. The noise of the receiver temperature is 1000 K at 800-900 GHz, 1200 K at 950 GHz, and 1600 K at 1.08 THz. The required (absorbed) local-oscillator power is —20 nW.
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Gousev YP, Olsson HK, Gol'tsman GN, Voronov BM, Gershenzon EM. NbN hot-electron mixer at radiation frequencies between 0.9 THz and 1.2 THz. In: Proc. 9th Int. Symp. Space Terahertz Technol.; 1998. p. 121–9.
Abstract: We report on noise temperature measurements for a NbN phonon-cooled hot-electron mixer at radiation frequencies between 0.9 THz and 1.2 THz. Radiation was coupled to the mixer, placed in a vacuum chamber of He cryostat, by means of a planar spiral antenna and a Si immersion lens. A backward-wave oscillator, tunable throughout the spectral range, delivered an output power of few 1.1W that was enough for optimum operation of the mixer. At 4.2 K ambient temperature and 1.025 THz radiation frequency, we obtained a receiver noise temperature of 1550 K despite of using a relatively noisy room-temperature amplifier at the intermediate frequency port. The noise temperature was fairly constant throughout the entire operation range and for intermediate frequencies from 1 GHz to 2 GHz.
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Yazoubov P, Kroug M, Merkel H, Kollberg E, Gol'tsman G, Lipatov A, et al. Quasioptical NbN phonon-cooled hot electron bolometric mixers with low optimal local oscillator power. In: Proc. 9th Int. Symp. Space Terahertz Technol.; 1998. p. 131–40.
Abstract: In this paper, the noise perform.ance of NIN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixers is investigated in the 0.55-1.1 THz frequency range. The best results of the DSB 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 a significant contribution to the measured noise temperature around 1.1 THz. The required LO power is typically about 60 nW. The frequency response of the spiral antenna+lens system is measured using a Fourier Transform Spectrometer with the HEB operating in a detector mode.
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Il'in KS, Cherednichenko SI, Gol'tsman GN, Currie M, Sobolewski R. Comparative study of the bandwidth of phonon-cooled NbN hot-electron bolometers in submillimeter and optical wavelength ranges. In: Proc. 9th Int. Symp. Space Terahertz Technol.; 1998. p. 323–30.
Abstract: We report the results of the bandwidth measurements of NbN hot-electron bolometers, perfomied in the terahertz frequency domain at 140 GHz and 660 GHz and in time domain in the optical range at the wavelength of 395 nm.. Our studies were done on 3.5-nm-thick NbN films evaporated on sapphire substrates and patterned into ilin-size microbridges. In order to measure the gain bandwidth, we used two identical BWOs (140 or 660 GHz), one functioning as a local oscillator and the other as a signal source. The bandwidth we achieved was 3.5-4 GHz at 4.2 K with the optimal LO and DC biases. Time-domain measurements with a resolution below 300 fs were performed using an electro-optic sampling system, in the temperature range between 4.2 K to 9 K at various values of the bias current and optical power. The obtained response time of the NbN hot-electron bolometer to —100- fs-wide Ti:sapphire laser pulses was about 27 ps, what corresponds to the 5.9 GHz gain bandwidth.
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Gao JR, Hajenius M, Baselmans JJA, Yang ZQ, Baryshev AM, Barends R, et al. Twin-slot antenna coupled NbN hot electron bolometer mixers for space applications. In: Proc. 9-th WMSCI. Vol 9. International Institute of Informatics and Systemics; 2005. p. 148–53.
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Cherednichenko S, Yagoubov P, Il'In K, Gol'tsman G, Gershenzon E. Large bandwidth of NbN phonon-cooled hot-electron bolometer mixers on sapphire substrates. In: Proc. 8th Int. Symp. Space Terahertz Technol.; 1997. p. 245–57.
Abstract: The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and film quality variation. The films, 2.5 to 10 mm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted of several parallel strips, each 1 1.1 wide and 211 long, placed between Ti-Au contact pads. To measure the gain bandwidth we used two identical BWOs operating in the 120-140 GHz frequency range, one functioning as a local oscillator and the other as a signal source. The majority of the measurements were made at an ambient temperature of 4.5 K with optimal LO and DC bias. The maximum 3 dB bandwidth (about 4 GHz) was achieved for the devices made of films which were 2.5-3.5 nm thick, had a high critical temperature, and high critical current density. A theoretical analysis of bandwidth for these mixers based on the two-temperature model gives a good description of the experimental results if one assumes that the electron temperature is equal to the critical temperature.
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Kawamura J, Blundell R, Tong C-YE, Gol'tsman G, Gershenzon E, Voronov B, et al. Phonon-cooled NbN HEB mixers for submillimeter wavelengths. In: Proc. 8th Int. Symp. Space Terahertz Technol.; 1997. p. 23–8.
Abstract: The noise performance of receivers incorporating NbN phonon-cooled superconducting hot electron bolometric mixers is measured from 200 GHz to 900 GHz. The mixer elements are thin-film (thickness — 4 nm) NbN with —5 to 40 pm area fabricated on crystalline quartz sub- strates. The receiver noise temperature from 200 GHz to 900 GHz demonstrates no unexpected degradation with increasing frequency, being roughly TRx ,; 1-2 K The best receiver noise temperatures are 410 K (DSB) at 430 GHz, 483 K at 636 GHz, and 1150 K at 800 GHz.
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