PPubMed24 Aug 2023Cited 135×

Single-photon detection in the mid-infrared up to 10 <i> μ </i> m wavelength using tungsten silicide superconducting nanowire detectors

V. B. Verma, B. Korzh, A. B. Walter, A. E. Lita, R. M. Briggs, M. Colangelo, Y. Zhai, E. E. Wollman, A. D. Beyer, J. P. Allmaras, H. Vora, D. Zhu, E. Schmidt, A. G. Kozorezov, K. K. Berggren, R. P. Mirin, S. W. Nam, M. D. Shaw

Abstract

'M. Colangelo' 'Y. Zhai' 'E. E. Wollman' 'A. D. Beyer' 'J. P. Allmaras' 'H. Vora' 'D. Zhu' 'E. Schmidt' 'A. G. Kozorezov' 'K. K. Berggren' 'R. P. Mirin' 'S. W. Nam' 'M. D. Shaw'] We developed superconducting nanowire single-photon detectors based on tungsten silicide, which show saturated internal detection efficiency up to a wavelength of 10 μm. These detectors are promising for applications in the mid-infrared requiring sub-nanosecond timing, ultra-high gain stability, low dark counts, and high efficiency, such as chemical sensing, LIDAR, dark matter searches, and exoplanet spectroscopy.

A figure from Single-photon detection in the mid-infrared up to 10 <i> μ </i> m wavelength using tungsten silicide superconducting nanowire detectors — fig. from the paper

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WSi superconducting nanowire detectors achieve saturated internal detection efficiency up to 10 µm mid‑infrared wavelengths.

What’s new

i.Demonstrated WSi SNSPDs with saturated internal detection efficiency up to 10 µm wavelength.
ii.Showed that increasing film resistivity via higher silicon content improves mid‑IR sensitivity.
iii.Fabricated and characterized nanowires of 50 nm and 70 nm widths operating at 0.85 K with QCL illumination.
iv.Provided analysis of scalability challenges and optical‑stack designs for higher system efficiency.

How they did it

The team co‑sputtered tungsten and silicon to create high‑resistivity WSi films with varied silicon content, patterned 10 µm‑long nanowires of 50–70 nm width, and measured photon count rates at 0.85 K using quantum cascade lasers at 4.8, 7.4, and 9.9 µm.

What they found

Internal detection efficiency saturated at 9.9 µm for 70 nm‑wide nanowires with 35 % ± 7 % Si film (Tc = 3.1 K, thickness = 3.2 nm).
Higher Si content (48 % ± 10 %) films (Tc = 2.8 K, thickness = 2.6 nm) showed improved saturation for all wavelengths and both 50 nm and 70 nm wires.
Background count rates remained low; dark counts limited by black‑body radiation.
Demonstrated operation at bias currents as low as 200 nA.

Caveats

✕Yield and scalability of 50–80 nm nanowires over large areas remain unproven.
✕Small active area limits coupling efficiency for practical mid‑IR applications.
✕System detection efficiency still requires optimized optical stack and filtering.
✕Performance at temperatures below 0.85 K was not investigated.

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