Temperature-Dependent Characterization of Large-Area Superconducting Microwire Array with Single-Photon Sensitivity in the Near-Infrared

TL;DR

The paper addresses the challenge of enabling large-area, near-infrared single-photon detection for low-background experiments. It presents a detailed temperature-dependent characterization of a 4-channel $1×1$ mm$^2$ WSi SMSPD array, measuring internal detection efficiency, time jitter, dark count rate, and cross-pixel coincidences. Key results include saturated IDE from 635 to 1650 nm, a time jitter of about $160$ ps at 1060 nm, and a DCR around $10^{-2}$ Hz at $0.2$ K, along with an excess of correlated dark counts across pixels. The observed coincidences imply a common background source (potentially cosmic muons), motivating background tagging and shielding strategies for dark matter experiments. This work provides a foundational dataset and methodology for deploying SMSPD arrays in low-background, near-infrared photon detection.

Abstract

Superconducting nanowire single photon detectors (SNSPDs) are a leading detector technology for time-resolved single-photon counting from the ultraviolet to the near-infrared regime. The recent advancement in single-photon sensitivity in micrometer-scale superconducting wires opens up promising opportunities to develop large area SNSPDs with applications in low background dark matter detection experiments. We present the first detailed temperature-dependent study of a 4-channel $1\times1$ mm$^{2}$ WSi superconducting microwire single photon detector (SMSPD) array, including the internal detection efficiency, dark count rate, and importantly the coincident dark counts across pixels. The detector shows saturated internal detection efficiency for photon wavelengths ranging from 635 nm to 1650 nm, time jitter of about 160 ps for 1060 nm photons, and a low dark count rate of about $10^{-2}$ Hz. Additionally, the coincidences of dark count rate across pixels are studied for the first time in detail, where we observed an excess of correlated dark counts, which has important implications for low background dark matter experiments. The results presented is the first step towards characterizing and developing SMSPD array systems and associated background for low background dark matter detection experiments.

Figures (9)

• Figure 1: An optical microscope image of the SMSPD under study is shown.
• Figure 2: Normalized PCR measured at 635 nm and 0.2 K for pixel 1, 2, and 3. Similar PCR curves observed for all pixels.
• Figure 3: Left: Normalized PCR measured at different wavelengths and at 0.2 K. Longer plateau for larger energy as expected. Right: Normalized PCR measured at different temperatures and at 635 nm. Similar onset for different temperatures, but longer plateaus for lower energy observed.
• Figure 4: Distribution of time difference between SMSPD signal and laser trigger for p3 measured at an operating temperature of 0.5 K and bias current of 0.165$\mu A$. The fitted $\sigma$ of the EMG distribution is $169\pm 5$ ps.
• Figure 5: Left: Time jitter with respect to bias current for all three pixels at 0.5 K. Right: Time jitter with respect to bias current for pixel 3 measured at different operating temperatures. The time jitter increases and varies at lower bias currents near the onset of detection efficiency, due to rapid changes and variations in the signal-to-noise ratio in that region.