Superconducting nanowire single photon detector with on-chip bandpass filter

TL;DR

This paper presents an integrated on-chip bandpass filter for superconducting nanowire single photon detectors, significantly reducing dark counts and enhancing detection efficiency by suppressing stray light and blackbody radiation.

Contribution

The authors designed and integrated a multilayer SiO2/Si bandpass filter onto SNSPDs, achieving a two-order reduction in dark counts and improved wavelength-sensitive detection performance.

Findings

Dark count rate reduced to sub-Hz levels

Detection efficiency of 56% at 1 Hz DCR

Minimal noise equivalent power of 2e-19 W/Hz^1/2

Abstract

Dark count rate is one of the key parameters limiting the performance of the superconducting nanowire single photon detector (SNSPD). We have designed a multi-layer film bandpass filter that can be integrated onto the SNSPD to suppress the dark counts contributed by the stray light and blackbody radiation of the fiber. The bandpass filter is composed of 16 SiO2/Si bilayers deposited onto the backside of a thermally oxidized Si substrate. The substrate shows an excellent bandpass filter effect and provides a high transmittance of 88% at the central wavelength of the pass band, which is the same as that of the bare substrate. The SNSPDs fabricated on the substrate integrated with the bandpass filter show conspicuous wavelength-sensitive detection efficiency. The background dark count rate is reduced by two orders of magnitude to sub-Hz compared with the conventional SNSPD (a few tens of Hz). The detector exhibits a system detection efficiency of 56% at DCR of 1 Hz, with the measured minimal noise equivalent power reaching 2e-19 w/Hz1/2.