Infrared photodetector based on the photofluxonic effect in superconducting thin films

摘要

The authors have recently proposed a new nonbolometric mechanism for detection of infrared photons in superconducting thin films, in which a photon nucleates the formation of a vortex- antivortex pair. This model predicts a limiting voltage responsivity of 1/(2ef), where f is the frequency of the radiation. Measurements on ultrathin NbN films at 4 K are reported which provide further evidence for this 'photofluxonic effect.' For $APEQ 0.1 $mu@W of red light (0.6 $mu@m), a responsivity of 6000 V/W of absorbed light has been measured, in agreement with the predictions. This response continues out to frequencies greater than 100 kHz, and is 1000 times greater than expected for a bolometric response. Preliminary measurements with 20 $mu@m infrared radiation also agree with this picture. Voltage noise in the absence of light was less than 1 nV/$ROOT@Hz, and was consistent with single-fluxon shot noise. Similar performance should also be possible using high-temperature superconductors. Some considerations for a fast, sensitive infrared detector based on these principles are presented.