Superconducting nanowire single-photon detector in an optical cavity for front-side illumination

We have integrated superconducting nanowire single-photon detectors (SNSPDs) with an optical cavity design for front-side illumination. Our optical cavity design increases the coupling efficiency of light to the nanowire detector and enables straightforward proximity fiber-coupling for a multichannel detector system. Using a confocal optical scanning technique, we measured a significantly enhanced optical absorptance of 73% in comparison with 20% in a typical bare nanowire device at 1550 nm and 3 K. Our method of fabrication of these devices on a silicon wafer and the local optical absorptance measurement are important steps toward developing next-generation SNSPD technology.