Superconducting tunnel junctions as detectors for ultraviolet, optical, and near infrared astronomy

Abstract

We discuss the capabilities of superconduct- ing tunnel junctions as detectors for ultraviolet, optical, and near-infrared astronomy. Such junctions have recently been shown to allow the detection of individual optical and ultraviolet photons with an inherent spectral resolu- tion related to the critical temperature of the absorbing superconductor. Limiting resolutions at 500 nm ranging from 5 { 40 nm (for materials with critical temperatures between 0.1 to 10 K) should be achievable. These detec- tors should have a high quantum eciency (> 50 per cent) over a very broad wavelength range from the ultraviolet to the near infrared (100 { 2000 nm). The overall e- ciency is limited by reflection from the superconducting lm, and should be improved signicantly by appropriate anti-reflection coatings. The devices function at very high incident photon rates|with count rates of order 10 kHz or higher being feasible, and photon arrival time data- tion possible to microsec-level accuracy. It is realistic in the future to envisage that these devices, of a size typi- cally 20 50 m 2 , could be packaged into imaging arrays. These key characteristics imply that many areas of optical and ultraviolet astronomy could benet signicantly from their further development.