Electro-optic comb-empowered measurement of the dynamic frequency of a laser

Abstract

Frequency-modulated lasers are widely used in spectroscopy, biology and LiDAR. The performance of these applications depends strongly on accurate tracking of the frequencies of frequency-modulated lasers. So far, real-time tracking of the frequencies of frequency-modulated lasers remains challenging. Here we propose dual electro-optic comb-based frequency tracking method by achieving integrated lithium niobate electro-optic combs with known carrier-envelope offset frequencies, arbitrarily tunable repetition rates and 29.45-nm bandwidth, enabling tracking of the frequencies of frequency-modulated lasers with a chirp rate up to 2 × 1018 Hz s−1, which is more than three orders of magnitude beyond the state of the art. Our method enabled frequency-modulated continuous wave ranging using a frequency-modulated laser with severe mode hops, nonlinearity and frequency overlapping. Our method lays the foundation for high-precision measurements of frequency, distance, and time using frequency-modulated lasers, enabling metrology with mode-hopping and high-chirp-rate frequency-modulated lasers. Using integrated lithium niobate electro-optic frequency combs with slightly different repetition rates, accurate tracking of the frequency variation in a frequency-modulated laser enables stable and high-precision 3D scene ranging.