FMCW LiDAR with precision approaching the quantum noise limit

Frequency-modulated continuous-wave laser LiDAR is a robust optical technology for long-range threedimensional distance and velocity measurement. However, inherent sweep chirp nonlinearity severely constrains distance resolution and precision. Conventional compensation methods fail to address residual nonlinearity, particularly in rapid, long-range measurement, posing a critical bottleneck to practical applications. Herein, we present a high-order nonlinear solving model and fundamentally compensate for residual nonlinearity, which can improve precision by one to two orders of magnitude over traditional methods. It yields 19.58 μm precision over 25 m for a non-cooperative target without resolution loss, even under experimental conditions where the absolute distance is overwhelmed by noise using traditional methods. This method exhibits robustness across various laser types and achieves precision near the quantum noise limit. This study lays the groundwork for more precise frequency-sweeping coherent detection technologies.