Micrometer-precision absolute distance measurement with a repetition-rate-locked soliton microcomb.

The soliton microcomb has sparked interest in high-precision distance measurement, owing to its ultrahigh repetition rate and chip-integrated scale. We report absolute distance measurements based on synthetic wavelength interferometry with a soliton microcomb. We stabilized the repetition rate of 48.98 GHz through injection locking, with fluctuations below 0.25 Hz. Distance measurements up to 64 mm were demonstrated, presenting residuals below 2.7 m compared with a referenced laser interferometer. Long-term distance measurements were made at two fixed positions of approximately 0.2 m and 1.4 m, resulting in a minimum Allan deviation as low as 56.2 nm at an average time of 0.05 s. The dynamic demonstration illustrated that the proposed system could track round-trip motion of 3 mm at speeds up to 100 mm/s. The proposed distance measurement system is, to our knowledge, the first microcomb-based synthetic wavelength interferometer and achieves a ranging precision of tens of nanometers, with potential applications in the fields of satellite formation flying, high-end manufacturing, and micro-nano processing.