BACK-SIDE REFLECTANCE OF HIGH T-C SUPERCONDUCTING THIN-FILMS IN THE FAR-INFRARED

We have measured the far-infrared reflectance of YBaCu3O7-delta high T -c superconducting (HTS) films, for radiation incident on the substrat e side (back- side illumination), in the spectral region from 15 to 65 0 cm(-1) and at temperatures between 10 and 300 K. The HTS films were deposited on Si substrates (with YSZ/CeO2 buffer layers) by pulsed las er ablation. The extremely large temperature dependence of the reflect ance experimentally demonstrates the feasibility of using HTS films to construct far-infrared intensity modulators. In this letter, we prese nt the measured results, as well as an analysis based on thin-film opt ics and a simple two-fluid model. (C) 1998 American Institute of Physi cs. [S0003-6951(98)04039-X].