NORMAL-STATE YBA2CU3OX FILMS - A NEW FAST THERMAL DETECTOR FOR FAR-INFRARED LASER-RADIATION WITH A UNIFORM WAVELENGTH RESPONSE

Room temperature YBa2Cu3Ox films, epitaxially grown on oriented substr ates, are shown to be effective detectors of far infrared laser pulses . The photovoltage arises due to an anisotropic material thermopower s ubject to the thermal gradient arising from the radiation heating. For a 40 nm thick film we have measured a responsivity of (5 +/- 2) X 10( -7) V/W, independent of frequency in the range from 20 to 110 cm(-1). The response time is limited by thermal diffusion, giving a 200 MHz de tector bandwidth and a noise equivalent power of 3.6 X 10(-3) W(Hz)(-1 /2) for this film thickness. Due to their large area (1 cm(2)) and uni form spectral response, such films may be useful replacements for pyro electric power/energy meters.