Detection Efficiency of a Spiral-Nanowire Superconducting Single-Photon Detector

TL;DR

This paper compares a spiral layout of superconducting nanowire single-photon detectors to traditional designs, showing improved detection efficiency especially in the infrared range, due to reduced susceptibility to critical current reduction at turns.

Contribution

It introduces a spiral design for SNSPDs that enhances detection efficiency and mitigates issues caused by sharp turns, with experimental validation across different nanowire widths.

Findings

Spiral SNSPD achieves 27.6% efficiency at 400-1700 nm.

Detection efficiency in the infrared range more than doubles compared to meander.

Spiral design reduces critical current reduction at turns.

Abstract

We investigate the detection efficiency of a spiral layout of a Superconducting Nanowire Single-Photon Detector (SNSPD). The design is less susceptible to the critical current reduction in sharp turns of the nanowire than the conventional meander design. Detector samples with different nanowire width from 300 to 100 nm are patterned from a 4 nm thick NbN film deposited on sapphire substrates. The critical current IC at 4.2 K for spiral, meander, and simple bridge structures is measured and compared. On the 100 nm wide samples, the detection efficiency is measured in the wavelength range 400-1700 nm and the cut-off wavelength of the hot-spot plateau is determined. In the optical range, the spiral detector reaches a detection efficiency of 27.6%, which is ~1.5 times the value of the meander. In the infrared range the detection efficiency is more than doubled.