Impact of Trapezoidal Cross Section on Polarization Sensitivity of SNSPD With Ultranarrow Nanowire

The superconducting nanowire single-photon detector (SNSPD) is inherently sensitive to polarization due to its anisotropic nanowire structure. We studied the polarization sensitivity of SNSPDs with ultranarrow nanowires (20-40 nm wide) by simulation and fabricated SNSPDs with 30-nm-wide nanowires. The SNSPD has a maximum system detection efficiency of 20% and a polarization extinction ratio (PER) of 18. The deviation of the PER between the experiment and the simulation can be explained by a trapezoidal cross section of the nanowire.