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Proceedings of Conferences

Session 5 "Superconductors at Microwaves"

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	Near-field nonlinear microwave microscope for study of superconductor properties (261.3 Kbytes) hot!	2004-06-29
Near-field nonlinear microwave microscope for study of superconductor properties M. A. Kucherenko, V. V. Kurin, Yu. N. Nozdrin, E. E. Pestov Institute for Physics of Microstructures RAS, 603950, Nizhniy Novgorod, GSP-105 Abstract – A near-field microwave microscope was developed to study third-harmonic response of high temperature superconductors (HTS). The initial wave frequency was 472 MHz and the nonlinear response was measured at 1.42 GHz. The temperature was changed from 77 to 92 K. The sensitivity of this system is 10^-14 W/Hz at 1.42 GHz. The scan of the film with a resolution of 125 μm was realized using this technique. The critical temperature spatial distribution was obtained and the quality of HTS films was specified based of the map of the third-harmonic response.
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	Third-order local nonlinear microwave response of superconductors (168.57 Kbytes) hot!	2004-06-29
Third-order local nonlinear microwave response of superconductors Evgeny E. Pestov, Vladislav V. Kurin, Yury N. Nozdrin, Alexander A. Andronov Institute for Physics of Microstructures, Russian Academy of Sciences, 603600, Nizhny Novgorod, GSP-105, Russia Abstract– Superconducting thin films continue to be of interest for passive device application at microwave frequencies, but nonlinear effects may limit their performance. We report a set of experimental data on local third-harmonic generation at microwave frequencies (0.5 GHz) in YBa₂Cu₃O₇ single crystals and thin films, and Nb thin films from 4.2 K to T_c. For local investigations of the nonlinear response a probe with inductive coupling was developed. The third-harmonic power is measured as a function of temperature and dc magnetic field in some places of the sample. The temperature dependence of the third-harmonic signal for YBa₂Cu₃O₇ single crystal and thin film features a number of peaks at temperatures of about 2/3 T_c . There is a strong dependence on an external dc magnetic field for the temperature dependence of the nonlinearity for Nb thin films.
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	Nonlinear microwave response and phase transitions in superconductor with multicomponent order param (162.99 Kbytes) hot!	2004-06-29
Nonlinear microwave response and phase transitions in superconductor with multicomponent order parameter Anatoly A. Utkin and Vladislav V. Kurin Institute for Physics of Microstructures, Russian Academy of Sciences, 603600, Nizhny Novgorod, GSP-105, Russia Abstract— A problem of nonlinear reflection of electromagnetic wave from a superconductive film was solved assuming a two component s and d superconductive order parameter. The magnitude of re-radiated wave with a frequency equal to three times the frequency of the incident wave (nonlinear response) was derived within the Ginsburg-Landau theory. A temperature dependence of the nonlinear response was analyzed for the different parameters of Ginsburg-Landau theory. A maximum of the nonlinear response at the temperatures of phase transition in between the “pure d<->mixed s and d phase” was predicted for the case of s±d symmetry of order parameter. For the case of s±id symmetry we found that the temperature dependence is gradually increasing close to the phase-transition temperatures.
		hits: 5618

	Low-noise NbN hot-electron bolometer mixer for operation at 2.5 and 3.8 THz (167.69 Kbytes) hot!	2004-06-29
Low-noise NbN hot-electron bolometer mixer for operation at 2.5 and 3.8 THz S. V. Antipov, Yu. B. Vachtomin, S. N. Maslennikov, K. V. Smirnov, N. S. Kaurova, Е. V. Grishina, B. M. Voronov, and G. N. Goltsman Radio-Physic Laboratory, Dept. of Physics, Moscow State Pedagogical University, 29 M.Pirogovskaia st., 119992, Moscow, Russia Introduction There are several atmospheric and astronomical international research projects such as SOFIA [1], TELIS [2], TREND [3], HERSCHEL-FIRST [4] aimed to the terahertz highresolution spectroscopy (up to 5 THz). To put the space-based and air-borne heterodyne instruments into operation at frequencies above 1 THz the superconducting NbN hot-electron bolometer (HEB) [5] will be incorporated into heterodyne receiver as a mixer. At the frequencies above 1.3 THz the sensitivity of the NbN HEB mixers outperform the one of the Schottky diodes and SIS-mixers, and the receiver noise temperature of the NbN HEB mixers increase with frequency following closely 10 - 20 hν/kB law. Besides, the NbN HEBMs have wide intermediate frequency (IF) band and require small local oscillator (LO) power (maximum 1µW). The IF gain bandwidth of such a mixer achieves 5 GHz [6,7]. At the 2.5 THz LO frequency, the best measured value of the double side band (DSB) noise temperature is 1400 K at T=4.2 K [7]. In this paper we present the results of the noise temperature measurements within one batch of NbN HEB mixers based on 3.5 nm thick superconducting NbN film grown on Si substrate with MgO buffer layer at the LO frequencies 2.5 THz and 3.8 THz. Such films show much better superconducting properties than NbN films grown on either Si or MgO substrates [8]. We also discuss the effect of the mixer dimensions on its noise temperature.
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	A novel superconducting single photon detector (272.09 Kbytes) hot!	2004-06-29
A novel superconducting single photon detector A. A. Korneev¹⁾, V. M. Matvienko¹⁾, P. B. Kouminov¹⁾, B.M. Voronov¹⁾, G. N. Gol’tsman¹⁾, A. Verevkin²⁾, R. Sobolewski²⁾ ¹⁾ Dept. of Physics, Moscow State Pedagogical University, 119992, Moscow, Russia ²⁾ Dept. of Electrical and Computer Engineering and Laboratory of Laser Energetics, University of Rochester, Rochester, NY 14627-0231 Abstract – We present the results of our recent study of the quantum efficiency (QE) in 0.56-1.55 µm wavelength range and dark counts rate of the simple in manufacture superconducting singe-photon detector (SSPD). The detector has been fabricated from ultrathin (4 nm-thick) NbN superconducting film patterned by electron beam lithography into meander-shaped 100 nm wide stripe covering 10x10 µm² active area. The advances in fabrication process allowed to improve the SSPD performance by reduction of the edge non-uniformity. Experimentally measured QE ranged from 7% for 1.55µm wavelength to 20% for visible light at 4.2K temperature and reached 23% for 1.3 µm wavelength at 2.0K temperature.
		hits: 5914

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