Performance of superconducting nanowire single photon detection system with different temperature variation

The performance of cryocooler-based superconducting single photon detection system suffers from the intrinsic temperature oscillation, which is typically ∼300 mK around 4.2 K originated from the periodic expansion of the cryocooler’s working fluid (He). By using a rare-earth alloy (ErNi) plate with a high heat capacity at cryogenic temperatures in between the cold head of the cryocooler and the detector block, the detector temperature variation is successfully damped to be less than 10 mK. The dark count rate is reduced and the maximum working bias current is increased. The quantum efficiency of SNSPD system is significantly improved by 40%.