High-resolution mid-infrared single-photon upconversion ranging

Single-photon laser ranging has widespread applications in remote sensing and target recognition.However,highly sensitive light detection and ranging(lidar)has long been restricted in the visible or near-infrared bands.An appealing quest is to extend the operation wavelength into the mid-infrared(MIR)region,which calls for an infrared photon-counting system at high detection sensitivity and precise temporal resolution.Here,we devise and demonstrate an MIR upconversion lidar based on nonlinear asynchronous optical sampling.Specifically,the infrared probe is interrogated in a nonlinear crystal by a train of pump pulses at a slightly different repetition rate,which favors temporal optical scanning at a picosecond timing resolution and a kilohertz refreshing rate over-50ns.Moreover,the cross-correlation upconversion trace is temporally stretched by a factor of 2×10^(4),which can thus be recorded by a low-bandwidth silicon detector.In combination with the time-correlated photon-counting technique,the achieved effective resolution is about two orders of magnitude better than the timing jitter of the detector itself,which facilitates a ranging precision of 4μm under a low detected flux of 8×10^(−5) photons per pulse.The presented MIR time-of-flight range finder is featured with single-photon sensitivity and high positioning resolution,which would be particularly useful in infrared sensing and imaging in photon-starved scenarios.