Two-micron-wavelength single-photon detection using the high-critical-current-bank structure superconducting wide...

Superconducting strip photon detector is a promising technology for achieving high detection efficiency around the 2000 nm wavelength region where exciting applications are expected in fields ranging from quantum science to atmospheric physics. However, improving the single-photon sensitivity usually requires narrower nanostrips, which necessitates advanced fabrication technologies. We demonstrate high-efficiency single-photon detection at 2000 nm using a 20-μm-wide superconducting strip, which is approximately 200 times wider than conventional nanostrips. By combining a high critical current bank (HCCB) structure that improves the wide strip's single-photon sensitivity with an optical cavity structure designed for the 2000 nm wavelength band, we realize system detection efficiency of 70% with near-unity internal detection efficiency. These results provide a high-productivity approach for high-performance single-photon detector development for the 2000 nm band.