Kuznesof, DanielAmer, NoureldinTaylor, Gregor G.Patel, Sahil R.Bumble, BruceCraiciu, IoanaChoudhary, NidhiChoi, BeomgyuMorozov, Dmitry V.Korzh, BorisShaw, Matthew D.Wollman, Emma E.Chong, YonukHadfield, Robert H.2025-10-282025-10-282025-10-272025-11-0310.1364/OE.5768612-s2.0-105019249412https://infoscience.epfl.ch/handle/20.500.14299/255296Mid-infrared (MIR) detection at the single-photon limit has become increasingly accessible, enabling applications in free-space communications, industrial sensing, astronomy, and biomedicine. However, direct time-correlated single photon-counting in the MIR remains a significant challenge. Here, we demonstrate single-pixel scanning light detection and ranging (LiDAR) at 3500 nm wavelength with sub-millimeter depth resolution in the single-photon regime, enabled by a differential impedance-matched tungsten silicide (WSi) superconducting nanowire single-photon detector (SNSPD), optimized for MIR detection, and an optical parametric oscillator (OPO) laser source. The detector’s exceptional timing performance is demonstrated by resolving sub-millimeter depth features of a target positioned 100 mm from the transceiver. In addition, we present the wavelength-dependent photoresponse and timing jitter of the device across a 1550–5438 nm wavelength range. The photon-counting MIR LiDAR system shown features extremely wide broadband operation, high timing performance, and single-photon sensitivity. This work demonstrates the potential of MIR time-correlated single photon-counting applications enabled by SNSPDs.truetext::journal::journal article::research article