Characterization of optical absorptance in superconducting nanowire single-photon detectors

We present a numerical simulation of the optical absorptance for the superconducting nanowire single-photon detectors (SNSPDs or SSPDs) designed with various layouts by using finite-element analysis software. The simulation results reveal that the electric field concentrated in the superconducting nanowire is enhanced by reducing the filling factor, and the degree of the enhancement becomes larger for thicker nanowires. Due to the large enhancement of the electric field in the nanowire with a double-side cavity structure, the high optical absorptance can be achieved even for the low-filling-factor layout by tuning the device design, which leads to the realization of SSPDs with high system detection efficiency and high counting rate.