A FAST INFRARED DETECTOR BASED ON PATTERNED YBCO THIN-FILM

Detectors for infrared radiation lambda = 0.85 mum) were made of 50 nm thick YBa2Cu3O7-delta films on LaAlO3 and MgO or 60 nm thick films on NdGaO3. Parallel strips (1 mum wide by 20 mum long) were patterned in the films and formed the active device. These devices were designed t o detect short infrared laser pulses by electron heating. The detector s were current biased into the resistive and the normal states. The re sponse was studied in direct pulse measurements as well as by amplitud e modulation of a laser. The pulse measurements showed a fast picoseco nd response followed by a slower decay related to phonon escape throug h the film-substrate interface and heat diffusion in the substrate. Th e frequency spectra up to 10 GHz showed two slopes with a knee corresp onding to the phonon escape time.