Broadband polarization insensitivity and high detection efficiency in high-fill-factor superconducting microwire single-photon detectors

Abstract

Single-photon detection via absorption in current-biased nanoscale superconducting structures has become a preferred technology in quantum optics and related fields. Single-mode fiber packaged devices have seen new records set in detection efficiency, timing jitter, recovery times, and the largest sustainable count rates. The popular approaches to decreasing polarization sensitivity have resorted to the deposition of a high-index dielectric layer in between the nanowires or the introduction of geometrically symmetric nanowire meanders, such as spirals and fractals, in the active area. The former method yields limited success, while constraints on bending radii, and by extension fill factors in the latter limits their maximum efficiency. The discovery of single-photon sensitivity in micrometer-scale superconducting wires enables novel meander patterns with no effective upper limit on the fill factor. This work demonstrates simultaneous low-polarization sensitivity (1.02 ± 0.008) and high detection efficiency (>91.8% to better than one standard deviation at 2 × 105 counts/s) across a 40 nm bandwidth centered at 1550 nm in 0.51 μm wide microwire devices made of silicon-rich tungsten silicide, sporting a new candelabra-style meander pattern with a fill factor of 0.91 in the active area. These devices boasted efficiencies of 96.5%–96.9% ± 0.5% at 1 × 105 counts/s for 1550 nm light.