Multispectral MoSi superconducting nanowire single photon detector

In this paper, a multispectral superconducting nanowire single photon detector (SNSPD) with high absorption efficiency is designed. It consists of Ag reflector, two SiO layers, Si slot and MoSi nanowire. Considering two typical quantum communication wavelengths (1310 nm and 1550 nm), when filling factor is 30 %, numerical simulation results show that the absorption efficiency of SNSPD can be over 95 % at each wavelength separately, and over 86 % at two target wavelengths simultaneously after introducing the second SiO layer and adjusting the structure parameters. And when filling factor is set to 40 %, the results at two target wavelengths are over 93 % and a broadband absorption (>80 %) of 1140 nm-1600 nm appears. In addition, the polarization sensitivity of the two-SiO-layers SNSPD is analyzed. When filling factor is over 63 %, the SNSPD attains both high absorption efficiency and TM-TE polarization insensitivity at two target wavelengths. The results of this work may provide access to fabricate high-efficiency and multispectral SNSPDs, and find applications in quantum optics and quantum communication systems.