A SENSITIVE YBACUO THIN-FILM BOLOMETER WITH ULTRAWIDE WAVELENGTH RESPONSE

We have constructed two types of high-temperature superconducting (HTSC) bolometers, whose performance is essentially wavelength independent from lambda approximately 0.6 to 450 mum: The first is a microbridge, of dimensions 20 X 20 mum, and the second is a meander, covering a region of approximately 1 mm2. Both were fabricated by photolithography of a superconducting YBaCuO thin film on SrTiO3. The bolometers are current biased, and the ac voltage induced by the chopped radiation is measured using lock-in detection. Operating optimally in the vicinity of the transition temperature (90 K), the first bolometer shows responsivity S approximately 1 mV/(W/cm2), while the second gives S approximately 800 V/W. The response of the first bolometer for various chopping frequencies is basically S approximately 1/square-root f, which makes it usable at frequencies up to > 50 kHz, while the second bolometer has a chopping-frequency response that is basically S approximately 1/f, with a cutoff frequency near 0.01 Hz.