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arXiv:2511.20868

Tungsten Germanide Superconducting Nanowire Single-Photon Detectors with Saturated Internal Detection Efficiency at Wavelengths up to 29 μm

Benedikt Hampel, Daniel Kuznesof, Andrew S. Mueller, Sahil R. Patel, Robert H. Hadfield, Emma E. Wollman, Matthew D. Shaw, Dirk Schwarzer, Alec M. Wodtke, Khalid Hossain, Allison V. Mis, Alexana Roshko, Richard P. Mirin, Sae Woo Nam, Martin J. Stevens, Varun B. Verma

physics.ins-detcond-mat.supr-conphysics.app-phphysics.opticsquant-phSubmitted Nov 25, 2025• Announced Nov 27, 2025• Revised Jun 16, 2026 (v2)
v1 · Nov 25, 2025v2 · Jun 16, 2026
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Abstract

Superconducting nanowire single-photon detectors (SNSPDs) are among the most sensitive single-photon detectors available and have the potential to transform fields ranging from infrared astrophysics to molecular spectroscopy. However, extending their performance into the mid-infrared spectral region - crucial for applications such as exoplanet transit spectroscopy and vibrational fingerprinting of molecules - has remained a major challenge, primarily due to material limitations and scalability constraints. Here, we report on the development of SNSPDs based on tungsten germanide, a novel material system that combines high mid-infrared sensitivity with compatibility for large-scale fabrication. Our detectors exhibit saturated internal detection efficiency at wavelengths up to 29 μm, while using 2.7x thicker films (8 nm vs 3 nm) and up to 4.5x wider nanowires (360 nm vs 80 nm) compared to mid-infrared-optimized SNSPDs fabricated from tungsten silicide. This advance will enable scalable, high-performance single-photon detection in a spectral region that was previously inaccessible, opening new frontiers in remote sensing, thermal imaging, environmental monitoring, molecular physics, and astronomy.

Journal reference
APL Photonics 11 (6): 066112 (2026)
DOI
10.1063/5.0331641
Comments
8 pages, 6 figures, Published in APL Photonics 11(6): 066112 (2026) (doi: 10.1063/5.0331641)

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Superconducting nanowire single-photon detectors (SNSPDs) are among the most sensitive single-photon detectors available and have the potential to transform fields ranging from infrared astrophysics to molecular spectroscopy. However, extending their performance into the mid-infrared spectral region - crucial for applications such as exoplanet transit spectroscopy and vibrational fingerprinting of molecules - has remained a major challenge, primarily due to material limitations and scalability constraints. Here, we report on the development of SNSPDs based on tungsten germanide, a novel material system that combines high mid-infrared sensitivity with compatibility for large-scale fabrication. Our detectors exhibit saturated internal detection efficiency at wavelengths up to 29 μm, while using 2.7x thicker films (8 nm vs 3 nm) and up to 4.5x wider nanowires (360 nm vs 80 nm) compared to mid-infrared-optimized SNSPDs fabricated from tungsten silicide. This advance will enable scalable, high-performance single-photon detection in a spectral region that was previously inaccessible, opening new frontiers in remote sensing, thermal imaging, environmental monitoring, molecular physics, and astronomy.
In this Letter, we characterized superconducting nanowire single-photon detectors (SNSPDs) based on amorphous tungsten germanide (W0.8Ge0.2) superconducting films, which exhibit superconducting properties comparable to those of amorphous WSi. The nanowire width ranges from 60 to 90 nm, with a fixed filling factor of 30%. All fabricated devices exhibit saturated intrinsic detection efficiency for infrared photons with wavelengths up to 2 μm, indicating that WGe is a promising candidate for SNSPDs designed for mid- and far-infrared photon detection. The timing jitter of these detectors, measured with a room-temperature amplifier, ranges from 127 to 234.5 ps. Further improvements can be achieved through device geometry optimization or the implementation of cryogenic amplifiers.
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