Optical response of highly oriented YBCO thin films

A thin-film transition edge bolometer was fabricated from laser ablated YBCO. The response to chopped 633-nm radiation was measured as a function of temperature, optical intensity, bias current, and signal frequency. At a chopping frequency of 1 Hz and a bias current of 100 mu A, the responsivity was 10 V/W and the noise power was 39 nW/ square root Hz. At low frequencies the device showed all the characteristics of a bolometer. At higher frequencies, however, an additional component of the photo response was found. The magnitude of this component scales roughly like f/sup -0.5/. This additional response is thought to be caused by optically induced depinning of vortices.