Detection Mechanism in SNSPD: Numerical Results of a Conceptually   Simple, Yet Powerful Detection Model
  In a recent publication we have proposed a numerical model that describes the detection process of optical photons in superconducting nanowire single-photon detectors (SNSPD). Here, we review this model and present a significant improvement that allows us to calculate more accurate current distributions for the inhomogeneous quasi-particle densities occurring after photon absorption. With this new algorithm we explore the detector response in standard NbN SNSPD for photons absorbed off-center and for 2-photon processes. We also discuss the outstanding performance of SNSPD based on WSi. Our numerical results indicate a different detection mechanism in WSi than in NbN or similar materials. 
Andreas Engel, Julia Lonsky, Xiaofu Zhang, Andreas Schilling
cond-mat.supr-con physics.ins-det