To facilitate high optical coupling efficiency and absorptance, the active area of a superconducting nano/microstrip single-photon detector (SNSPD/SMSPD) is often designed as a meander configuration with a high filling factor (e.g., >=0.5). However, the switching current (Isw) of SNSPD/SMSPD, at which the detector switches into the normal state, is significantly suppressed by a geometry-induced "current crowding effect", where there are sharp bends in the strip. Here we propose and experimentally verify an alternative method to reduce current crowding both in SNSPD and SMSPD by directly increasing the thickness of the bends through the deposition and lift-off of a secondary superconducting film. We measure and compare the performance of SNSPDs and SMSPDs with different filling factors and bend configurations, with or without thickened bends. Improvements for detectors were observed in detection efficiency, intrinsic dark count rate, and time jitter, owing to the enhanced Isw. Our method provides a promising way of optimizing SNSPD/SMSPD detection performance.
@article{arxiv.2112.08009,
title = {Reducing current crowding in meander superconducting strip single-photon detectors by thickening bends},
author = {Jia-Min Xiong and Wei-Jun Zhang and Guang-Zhao Xu and Li-Xing You and Xing-Yu Zhang and Lu Zhang and Cheng-Jun Zhang and Dong-Hui Fan and Yu-Ze Wang and Hao Li and Zhen Wang},
journal= {arXiv preprint arXiv:2112.08009},
year = {2021}
}