NbN Superconducting Single-Photon Detector with Bilayer Structure

We fabricated a superconducting single-photon detector (SSPD) with bilayer structure. The detector consists of two meanders which are superposed face-to-face using optical adhesive. When the two nanowires are superposed perpendicularly, the degree of linear polarization dependence is reduced from 0.16 to 0.000617. This means that the polarization dependence, which has been a drawback in SSPDs, is suppressed almost completely using the present structure.