Fig. 1: The schematic diagram of the chaotic-QFC LiDAR and its various stages.

a Overview, b the spectrum of the DFG pump (blue) light and ASE (green) before the DFG process, c the spectrum of the probe (yellow), reference (green), and DFG pump light after the DFG process, d the spectrum of the reference and collected probe light back-scattering (mixed with noise), e the spectrum of the reference light, depleted probe light, c-SFG peak (red arrow) and unfiltered i-SFG (red curve) background, (f) the narrowband optical filtering of i-SFG, g the homodyne beating frequency fHDD between the DFG pump light and frequency shifted c-SFG.