Optical and thermal performance advantages for silicon substrates in ybco bolometer devices

We review recent progress we have made in the fabrication of epitaxial YBCO thin-film bolometers (photothermal infrared detectors) on Si wafers. IR transmission of the Si substrates, YSZ buffer layers on Si, and YBCO/YSZ/Si have been measured from the near (A/-1 urn) to the far IR (-500 pm) at low temperatures. These show Si to be very superior to other available choices of substrate for epitaxial-YBCO film bolometers. We also show, by various wafer fabrications, that the high strength and thermal conductivity of Si can be exploited to considerably reduce the device thermal-equilibration time, when irradiated with weak IR pulses, and concomitantly increase the device sensitivity. Further, we have fabricated monolithic quad arrays of bolometers, and find excellent element-to-element uniformity in their transitions and in their function as detectors for Fourier-Transform IR (FTTR) spectroscopy. We have also recently fabricated an epitaxial YBCO-film bolometer on a submicron-thick window in a Si wafer, the first such device known, to us. The rise and fall times (10-90%) were less than 500 us, under chopped IR illumination.