Enhancing spectral sensitivity and scalability of superconducting nanowire photon detectors: mid-infrared characterization and near-infrared integration

We present enhancements in the spectral sensitivity and scalability of superconducting nanowire single-photon detectors based on U-shaped NbTiN nanowires. Designed on a silicon-on-insulator photonic platform, our detectors exhibit near-unity internal detection efficiency under flood illumination across wavelengths from 1550nm to 3502nm. Additionally, we demonstrate arrays of waveguide-integrated superconducting nanowire single-photon detectors optimized for operation at 1550nm. Cryogenic light coupling to the arrays is achieved through a photonic wire bonding technique, enabling low-loss coupling and high-density integration, thereby facilitating the scaling of detector counts per cryostat for near-infrared applications.