Dual-comb-based multi-axis time-of-flight measurement via high-efficiency optical cross-correlation in a semiconductor optical amplifier

Absolute distance measurement for multiple targets is required in industrial and scientific fields such as machine monitoring, detection of distortion in large structures, wafer alignment in semiconductor manufacturing, and the formation flying of satellites. Furthermore, the expansion of measurement channels is essential for the effective application of multi-target measurement. However, because measurement channels' expansion requires high power, it is difficult due to the low conversion efficiency of conventional systems that use a non-linear crystal for optical cross-correlation. In this study, for measurement channel expansion, time-of-flight based absolute laser ranging via high-efficiency dual-comb cross-correlation using a semiconductor optical amplifier is developed. The semiconductor optical amplifier acts as a cross-correlator, and it can produce a cross-correlation signal with a laser’s power of 50 µW because of its very high conversion efficiency. This method is suitable for expanding the measurement channels and measuring non-cooperative targets as it can detect low-power signals. The repeatability of the distance measurement is 4 µm at a single shot (37 µs) and 120 nm for 5 ms. The linearity is assessed by evaluating the R-square, which is equal to 1 within the range of significant figures. Moreover, the distance measurement of targets lying on the two axes was demonstrated to ensure the measurement channels' expansion. This measurement system has the potential to determine multiple distances, making it applicable to diverse fields such as semiconductor manufacturing, smart factories, plant engineering, and satellite formation flying.