79-GHz acquisition rate absolute distance measurement with lithium niobate electro-optic comb

AI-empowered autonomous vehicles must sense the fast-changing three-dimensional environments with high speed and precision. However, the tradeoff between acquisition rate and non-ambiguity range prevents most LiDARs from achieving high-speed absolute distance measurement. Here we demonstrate a lithium niobate electro-optic comb-enabled ultrafast absolute distance measurement method — repetition rate-modulated frequency comb (RRMFC). We achieved an integrated lithium-niobate phase modulator with a half-wave voltage of 1.47 V, leading to over 50 sidebands and a repetition rate can be tuned over 12 GHz in 4 μs. Leveraging these unique features, RRMFC can coherently measure the distance by detecting interference peaks in the time domain, leading to acquisition rates up to 1.79 GHz and a large non-ambiguity range. This single-channel acquisition rate is over 4 orders of magnitude higher than the state-of-the-art absolute distance measurement system. Thus, RRMFC-based LiDAR allows autonomous vehicles to sense the fine details of a fast-changing environment using a single laser. Most LiDARs have an intrinsic tradeoff between acquisition rate and non-ambiguity range. Researchers demonstrated a LiDAR called RRMFC based on an integrated lithium niobate frequency comb, leading to a 1.79 GHz acquisition rate and infinite non-ambiguity range.