Danerud, M., Winkler, D., Lindgren, M., Zorin, M., Trifonov, V., Karasik, B., et al. (1994). A fast infrared detector based on patterned YBCO thin film. Supercond. Sci. Technol., 7(5), 321–323.
Abstract: Detectors for infrared radiation ( lambda =0.85 mu m) were made of 50 nm thick YBa2Cu3O7- delta films on LaAlO3 and MgO or 60 nm thick films on NdGaO3. Parallel strips (1 mu m wide by 20 mu m long) were patterned in the films and formed the active device. These devices were designed to detect short infrared laser pulses by electron heating. The detectors were current biased into the resistive and the normal states. The response was studied in direct pulse measurements as well as by amplitude modulation of a laser. The pulse measurements showed a fast picosecond response followed by a slower decay related to phonon escape through the film-substrate interface and heat diffusion in the substrate. The frequency spectra up to 10 GHz showed two slopes with a knee corresponding to the phonon escape time.
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Gershenzon, E. M., Gol’tsman, G. N., Sergeev, A., & Semenov, A. D. (1990). Picosecond response of YBaCuO films to electromagnetic radiation. In W. Gorzkowski, M. Gutowski, A. Reich, & H. Szymczak (Eds.), Proc. European Conf. High-Tc Thin Films and Single Crystals (pp. 457–462).
Abstract: Radiation-induced change of the resistance was studied in the resistive state of YBaCuO films. Electron-phonon relaxation time T h was determmed from direct ep measurements and analysis of quasistationary electron heating. Temperature dependence of That TS 40 K was found to – ep be T h.. T'. The resul ts show that ep detectors with the response time of few picosecond at nitrogen temperature can be realized.
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Gershenzon, E. M., Gol'tsman, G. N., Semenov, A. D., & Sergeev, A. V. (1990). Mechanism of picosecond response of granular YBaCuO films to electromagnetic radiation. Solid State Communications, 76(4), 493–497.
Abstract: The ultrafast mechanisms of radiation detection in granular YBaCuO films are studied in the wide wavelength range from millimeter to near infrared. With the rise of radiation frequency the Josephson detection at the grain boundary weak links is replaced by electron heating into the grains. This change occurs in the submillimeter wavelength range. Electron-phonon relaxation time τeph is determined by direct measurements and analyses quasistationary electron heating. Temperature dependence of τeph at T ≤ 40 K was found to be τeph ∼ T−1. The results show that detectors with the response time of few picoseconds at nitrogen temperature are attainable.
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Semenov, A. D., Goghidze, I. G., Gol’tsman, G. N., Sergeev, A. V., & Gershenzon, E. M. (1993). Evidence for the spectral dependence of nonequilibrium picosecond photoresponse of YBaCuO thin films. Appl. Phys. Lett., 63(5), 681–683.
Abstract: The transient voltage photoresponse of current biased YBaCuO thin films to 20 ps laser pulses of 0.63 and 1.54 μm wavelengths is measured for temperatures around the superconducting transition region. The fast picosecond decay of the response is followed by a slow nanosecond relaxation which is associated with the bolometric effect. The magnitude of the fast component of the response varies in proportion to the square root of wavelength that plausibly reflects multiplication processes of photoexcited electrons via electron–electron scattering and interaction with high energy phonons.
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Gol'tsman, G. N., Goghidze, I. G., Kouminov, P. B., Karasik, B. S., Semenov, A. D., & Gershenzon, E. M. (1994). Influence of grain boundary weak links on the nonequilibrium response of YBaCuO thin films to short laser pulses. J. Supercond., 7(4), 751–755.
Abstract: The transient voltage response in both epitaxial and granular YBaCuO thin films to 80 ps pulses of YAG∶Nd laser radiation of wavelength 0.63 and 1.54 μm was studied. In the normal and resistive states both types of films demonstrate two components: a nonequilibrium picosecond component and a bolometric nanosecond one. The normalized amplitudes are almost the same for all films. In the superconducting state we observed a kinetic inductive response and two-component shape after integration. The normalized amplitude of the response in granular films is up to five orders of magnitude larger than in epitaxial films. We interpret the nonequilibrium response in terms of a suppression of the order parameter by the excess of quasiparticles followed by the change of resistance in the normal and resistive states or kinetic inductance in the superconducting state. The sharp rise of inductive response in granular films is explained both by a diminishing of the cross section for current percolation through the disordered network of Josephson weak links and by a decrease of condensate density in neighboring regions.
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