Pushing the limits of midwave infrared detection with superconducting nanowire single-photon detectors

Superconducting nanowire single-photon detectors (SNSPDs) have emerged as the gold standard in light detection in the visible and near-IR ranges, offering near-unity detection efficiency, high temporal precision, and a very low dark count rate. Extending these single-photon detection capabilities into wavelengths beyond 2 μm is expected to have far-reaching implications for long-wavelength quantum optics, communication, and computing. Beyond quantum, long-wavelength SNSPDs are expected to impact fields currently limited by detectors with high background levels and relatively poor temporal resolution and detection efficiency. Examples include exploiting underutilized atmospheric windows beyond 2 μm for free-space communication and venturing into the molecular vibrational spectroscopy regime to prob weak signals of chemical species in astronomy, environmental monitoring, and fundamental molecular studies. We showcase the development of externally fiber-coupled short-wave infrared (2.0-2.3 μm) and mid-wave infrared (3.0-3.4 μm) SNSPDs. Across both wavelength ranges, we venture beyond state-of-the-art and demonstrate the best-reported system detection efficiencies and specific detectivities. We discuss the inherent advantages and challenges in IR detection based on superconductors and showcase how the newly developed SNSPDs can be used to characterize emerging materials platforms and quantum emitters in a previously unattainable manner.