Superconducting nanowire single photon detector with on-chip bandpass filter

摘要

Dark count rate is one of the key parameters limiting the performance of thesuperconducting nanowire single photon detector (SNSPD). We have designed amulti-layer film bandpass filter that can be integrated onto the SNSPD tosuppress the dark counts contributed by the stray light and blackbody radiationof the fiber. The bandpass filter is composed of 16 SiO2/Si bilayers depositedonto the backside of a thermally oxidized Si substrate. The substrate shows anexcellent bandpass filter effect and provides a high transmittance of 88% atthe central wavelength of the pass band, which is the same as that of the baresubstrate. The SNSPDs fabricated on the substrate integrated with the bandpassfilter show conspicuous wavelength-sensitive detection efficiency. Thebackground dark count rate is reduced by two orders of magnitude to sub-Hzcompared with the conventional SNSPD (a few tens of Hz). The detector exhibitsa system detection efficiency of 56% at DCR of 1 Hz, with the measured minimalnoise equivalent power reaching 2e-19 w/Hz1/2.