High-precision dual-comb ranging based on two-color nonlinear asynchronous optical sampling

Dual-comb ranging (DCR) is a powerful technique for high-precision distance measurement. DCR based on nonlinear asynchronous optical sampling (ASOPS) is practical for field applications, since it does not require mutually coherent optical frequency combs. However, high laser power is usually needed for nonlinear frequency conversion. To alleviate this issue, we introduce a DCR method based on two-color nonlinear ASOPS by utilizing efficient Type-0 phase matching in a periodically poled lithium niobate (PPLN) crystal. In the experiment, a pair of mode-locked Er-fiber lasers centered at 1540 nm and 1580 nm were used to generate a sum frequency signal at 780 nm, which was selected by a narrow bandpass filter for background-free time-of-flight (ToF) measurements. We achieved < 3 µm ranging precision at 100 ms acquisition time with an echoed laser power of 5 µW. The dynamic performance was confirmed by tracking a moving translation stage.