Improved performance of a superconductive optical detector with planar antennas

A significant improvement in performance of an ultrathin-film NbN superconductive infrared detector was demonstrated by using a planar antenna concept. The output signal voltage is increased through improved optical coupling and the detector noise is decreased by reducing the total area of the NbN detector element. An enhancement in the signal-to-noise ratio by 32 dB was observed when comparing antenna-coupled detectors to area detectors (e.g., meandering lines). In addition, the authors observed a polarization selectivity of about 13 dB to linearly polarized light, which can provide additional discrimination. The primary noise mechanism in these films is confirmed to be voltage shot noise due to fluctuations in the motion of flux quanta in the film. This is a precise dual to current shot noise. >