  Light detection and ranging (LiDAR) has emerged as an indispensable tool in
autonomous technology. Among its various techniques, frequency modulated
continuous wave (FMCW) LiDAR stands out due to its capability to operate with
ultralow return power, immunity to unwanted light, and simultaneous acquisition
of distance and velocity. However, achieving a rapid update rate with
sub-micron precision remains a challenge for FMCW LiDARs. Here, we present such
a LiDAR with a sub-10 nm precision and a 24.6 kHz update rate by combining a
broadband Fourier domain mode-locked (FDML) laser with a silicon nitride
soliton microcomb. An ultrahigh frequency chirp rate up to 320 PHz/s is
linearized by a 50 GHz microcomb to reach this performance. Our theoretical
analysis also contributes to resolving the challenge of FMCW velocity
measurements with nonlinear frequency sweeps and enables us to realize velocity
measurement with an uncertainty below 0.4 mm/s. Our work shows how nanophotonic
microcombs can unlock the potential of ultrafast frequency sweeping lasers for
applications including LiDAR, optical coherence tomography and sensing.
