Wavelength dependence of intrinsic detection efficiency of NbN superconducting nanowire single-photon detector**Project supported by the National Key R&D Program of China (Grant No. 2017YFA0304000), the National Natural Science Foundation of China (Grant Nos. 61671438 and 61827823), the Science and Technology Commission of Shanghai Municipality, China (Grant No. 16JC1400402), Program of Shanghai Academic/Technology Research Leader, China (Grant No. 18XD1404600), and the

Abstract

Superconducting nanowire single-photon detectors (SNSPDs) have attracted considerable attention owing to their excellent detection performance; however, the underlying physics of the detection process is still unclear. In this study, we investigate the wavelength dependence of the intrinsic detection efficiency (IDE) for NbN SNSPDs. We fabricate various NbN SNSPDs with linewidths ranging from 30 nm to 140 nm. Then, for each detector, the IDE curves as a function of bias current for different incident photon wavelengths of 510–1700 nm are obtained. From the IDE curves, the relations between photon energy and bias current at a certain IDE are extracted. The results exhibit clear nonlinear energy–current relations for the NbN detectors, indicating that a detection model only considering quasiparticle diffusion is unsuitable for the meander-type NbN-based SNSPDs. Our work provides additional experimental data on SNSPD detection mechanism and may serve as an interesting reference for further investigation.