Detection of optical photons with superconducting tunnel junction detectors

High quality, Nb based Superconducting Tunnel Junction Detectors (STJDs) have been successfully used for the detection of single photons, in the visible and UV, from 200 to 500 nm. The detectors, operating at a temperature of about 0.4 K, have shown excellent response linearity and good wavelength discrimination, with a typical device limited resolution of order 20% over the measured range. The high quantum efficiency (of order 50%), the very high temporal resolution and the single photon counting capability, coupled to a wavelength discrimination demonstrated by STJDs, are very important characteristics for the development of a completely new generation of optical detectors. The development of an optical camera based on STJDs has been initiated and preliminary design solutions are reported.