Optical response of epitaxial and granular films of YBa/sub 2/Cu/sub 3/O/sub 7- delta / at temperatures from 25 K to 100 K

The authors present the results of optical detection in epitaxial and granular films of YBa/sub 2/Cu/sub 3/O/sub 7- delta / at wavelengths of 0.63, 3.39, and 10.6 mu m and at temperatures from 25 K to 100 K. Both types of film exhibit only bolometric detection, with no evidence for nonequilibrium effects in this temperature range. For 0.63- mu m radiation, mechanically chopped at 725 Hz, measurements of a 10*90 mu m/sup 2/ epitaxial bridge yield a bolometric responsivity of approximately 4*10/sup 3/ V/W, and detectivity D* of more than 10/sup 8/ cm square root Hz/W. Granular films biased above their critical current are found to exhibit two-level switching noise, resulting in Lorentzian deviations from an otherwise 1/f noise spectrum.<
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