Two-photon dual-comb LiDAR for precision ranging to non-optical targets

Two-photon dual-comb LiDAR (2phDCL) provides time-of-flight ranging at kHz update rates, with instantaneous precisions of a few µm, and a data burden orders of magnitude lower than interferometric dual-comb methods. These capabilities make 2phDCL of interest for industrial applications where ranging to uncooperative surfaces is required. In this invited article, we present the first extension of 2phDCL ranging to non-cooperative targets, specifically demonstrating results from tin, brass, aluminium and stainless steel surfaces. An amplified detection scheme with 60 µW sensitivity is shown to mitigate the lower optical power returned from the rolled or brushed surfaces of these metals. We perform ranging from a few cm up to 1 m, with around 5 µm instantaneous precisions and demonstrate one-dimensional metrology of structured metal artefacts.