Analysis of coherent laser echo characteristics back scattered from rough Gaussian target

Abstract

The surface property of rough target can cause the decoherence and depolarization effects, which is among the main limiting factors in heterodyne detection. In the decoherence analyses, the phase fluctuation model of laser echo from rough target is established based on the spectral density method, and the phase fluctuations under typical roughness conditions are obtained by Monte Carlo method. The distribution properties of heterodyne signal amplitudes are analyzed under different surface height fluctuation σ and correlation length T. Then the corresponding experiments are carried out, which show that the phase fluctuations of laser echo satisfy the Gaussian distribution, and the decoherence effect induces the reductions and fluctuations of heterodyne signal amplitudes, especially with larger roughness surface. For typical rough metal targets, the depolarization characteristics of laser echoes from different scattering positions are obtained, which suggest that the depolarization effect increases with the rise of roughness. The positive correlation between the decoherence and depolarization effects provides a reference for the design of heterodyne lidar system, and the statistics can also be adopted for target roughness inference and target type identification.