Cryogenic Dielectric Metasurface‐Integrated Superconducting Nanowire Single‐Photon Detectors

ABSTRACT Over the past decade, multielement superconducting nanowire single‐photon detectors (SNSPDs) have emerged as the leading single‐photon detection technology due to their exceptional system detection efficiency (SDE), ultrahigh timing precision, and negligible dark counts. However, achieving these performances with a single‐element SNSPD has been an outstanding challenge due to a fundamental trade‐off: A large active area is necessary for high SDE, whereas a smaller area is crucial for higher photon count rates, lower dark counts, and lower jitter. Here, we introduce a dielectric cryogenic metalens integrated with a single‐element SNSPD to achieve high SDE with a smaller active area. We report a 77‐fold enhancement in the SDE of a metalensed SNSPD with a 5 m 5 m active area, compared with an identical reference SNSPD without a metalens, using a moderately sized 60 m 60 m metalens. Next, we theoretically demonstrate polarization‐resolved photodetection at the telecommunication wavelength using a bifunctional metalens. We achieve a cross‐detection probability of 2 between metalensed SNSPDs spaced at 10 m under illumination with x ‐ and y ‐polarized light. Integrating a multifunctional cryogenic metasurface with the state‐of‐the‐art SNSPDs may enable novel capabilities with reduced size, weight, power, cost, and cooling (SWaP‐) requirements.