Optical detector using superconducting BaPb0.7Bi0.3O3 thin films

This paper describes a highly sensitive optical detector using a perovskite-type superconductor, BaPb0.7Bi0.3O3 (BPB) thin film. Optical signals create quasiparticles and induce changes in the superconducting energy gap. These changes are measured by tunnel junctions which are formed along the grain boundaries in the BPB polycrystalline thin film. The detector sensitivity is about 104 V/W in the 1–8-μm wavelength range, and the detector is found to be capable of responding up to 1.3 GHz at the 1.3-μm wavelength. Consequently, this BPB detector is well suited in infrared spectrometer and optical-communications system applications.