Karasik BS, Milostnaya II, Zorin MA, Elantev AI, Gol'tsman GN, Gershenzon EM. High speed current switching of homogeneous YBaCuO film between superconducting and resistive states. IEEE Trans Appl Supercond. 1995;5(2):3042–5.
Abstract: Transitions of thin structured YBaCuO films from superconducting (S) to normal (N) state and back induced by a supercritical current pulse has been studied. A subnanosecond stage in the film resistance dynamic has been observed. A more gradual (nanosecond) ramp in the time dependence of the resistance follows the fast stage. The fraction of the film resistance which is attained during the fast S-N stage rises with the current amplitude. Subnanosecond N-S switching is more pronounced for smaller amplitudes of driving current and for shorter pulses. The phenomena observed are viewed within the framework of an electron heating model. The expected switching time and repetition rate of an optimized current controlling device are estimated to be 1-2 ps and 80 GHz respectively.
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Zorin M, Gol'tsman GN, Karasik BS, Elantev AI, Gershenzon EM, Lindgren M, et al. Optical mixing in thin YBa2Cu3O7-x films. IEEE Trans Appl Supercond. 1995;5(2):2431–4.
Abstract: High quality, j/sub c/ (77 K)>10/sup 6/ A/cm/sup 2/, epitaxial YBa2Cu3O7-x films of 50 nm thickness were patterned into ten parallel 1 /spl mu/m wide strips. The film structure was coupled to a single-mode fiber. Mixer response was obtained at 0.78 /spl mu/m using laser frequency modulation and an optical delay line. Using two semiconductor lasers at 1.55 /spl mu/m wavelength the beating signal was used to measure the photoresponse up to 18 GHz. Nonequilibrium photoresponse in the resistive state of the superconductor was observed. Bolometric response dominates up to 3 GHz, after which the nonequilibrium response is constant up to the frequency limit of our registration system. Using an electron heating model the influence of different thermal processes on the conversion loss has been analyzed. Ways of increasing the sensitivity are also discussed.
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Gousev YP, Gol'tsman GN, Karasik BS, Gershenzon EM, Semenov AD, Barowski HS, et al. Quasioptical superconducting hot electron bolometer for submillmeter waves. Int J of Infrared and Millimeter Waves. 1996;17(2):317–31.
Abstract: We report on a superconducting hot electron bolometer coupled to radiation via a broadband antenna. The bolometer, a structured NbN film, was patterned on a thin dielectric membrane between terminals of a gold slotline antenna. We investigated the response to submillimeter radiation (wave-lengths ∼ 0.1 mm to 0.7 mm) in the fundamental Gaussian mode. We found that the directivity of the antenna was constant within a factor of 2.5 through the whole experimental range. The noise equivalent power of the bolometer at 119 µm was ∼ 3 · 10−13 W/Hz1/2; a time constant of ∼ 160 ps was estimated.
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Gerecht E, Musante CF, Wang Z, Yngvesson KS, Mueller ER, Waldman J, et al. Optimization of hot eleciron bolometer mixing efficiency in NbN at 119 micrometer wavelength. In: Proc. 7th Int. Symp. Space Terahertz Technol.; 1996. p. 584–600.
Abstract: We describe an investigation of a NbN HEB mixer for 2.5 THz. An intrinsic conversion loss of 23 dB has been measured with a two-laser measurement technique. The conversion loss was limited by the LO power available and is expected to decrease to 10 dB or less when sufficient LO power is available. For this initial experiment we used a prototype device which is directly coupled to the laser beams. We present results for a back-short technique that improves the optical coupling to the device and describe our progress for an antenna-coupled device with a smaller dimension. Based on our measured data for conversion loss and device output noise level, we predict that NbN HEB mixers will be capable of achieving DSB receiver noise temperatures of ten times the quantum noise limit in the THz range.
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Trifonov VA, Karasik BS, Zorin MA, Gol'tsman GN, Gershenzon EM, Lindgren M, et al. 9.6 μm wavelength mixing in a patterned YBa2Cu3O7-δ thin film. In: Proc. 7th Int. Symp. Space Terahertz Technol.; 1996. p. 337–48.
Abstract: Hot-electron bolometric (HEB) mixing of 9.6 gm infrared radiation from two lasers in high-quality YBa2Cu307_3 (YBCO) patterned thin film has been demonstrated. A heterodyne measurement showed an intermediate frequency (IF) bandwidth of 18 GHz, limited by our measurement system. An intrinsic limit of 100 GHz is predicted. Between 0.1 and 1 GHz intermediate frequency, temperature fluctuations with an equivalent output noise temperature Tfl up to -150 K, contributed to the mixer noise while Johnson noise dominated above 1 GHz. The overall conversion loss at 77 K at low intermediate frequencies was measured to be -25 dB, of which 13 dB was due to the coupling loss. The IIEB mixer is very promising for use in heterodyne receivers within the whole infrared range.
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