Fiber‐Integrated Stacking Superconducting Nanowire Single‐Photon Detectors With Orthogonal Polarization Sensitivity and Coincidence Detection

Although photodetector integration on waveguides is advanced, optical fiber lacks advantages in integration scalability. Integrating multiple photodetectors enables multi‐dimensional photon information acquisition, which is crucial for quantum information science. Here, fiber‐integrated dual‐layer SNSPDs with orthogonal polarization sensitivity and coincidence detection capability are demonstrated. Two SNSPD membranes were sequentially transferred onto a fiber facet with orthogonal nanowire orientations. At 1550 nm, the top and bottom layers exhibited system detection efficiency (SDE) of 49.6% and 42.4%, and polarization extinction ratio (PER), which is defined as the ratio of the maximum to minimum SDE, of 3.94 and 4.37, respectively. Summing the two signals increased the system detection efficiency to 57.9%–60.7% and reduced the overall PER to 1.06–1.14 across 1480–1640 nm. By reading each layer individually, coincidence measurement can be performed directly within the fiber with an overall timing jitter of 86 ps, characterized by femtosecond laser pulses. This work demonstrates multi‐dimensional single‐photon detection and the potential for fiber‐integrated quantum circuits.