Statistic and coherent properties of scattered light fields for different geometrical parameters of rough surfaces

Abstract

The relation between the correlation and coherent properties of light fields scattered by rough surfaces and the geometrical parameters of these surfaces is analysed. It is shown that, if the coherence time of illuminating radiation is τc>10ω0 (where ω0 is the central frequency of the emission spectrum), then, by averaging the field intensity scattered by a rough surface over time T>10τc , we can determine the stationary regions and coherent parameters of the scattered field and the conditions imposed on the narrowband and chromatic (spectral) parameters of illuminating radiation. These regions, parameters, and conditions are specified by the following parameters: the coherence length Lc=τcc of illuminating radiation, the transverse size d of the backscattering region of the surface, the depth Ls of the backscattering region, the distance rc from a receiving aperture to the surface, the size dρ of the receiving aperture, the central wavelength λ0=c/ω0 of illuminating radiation, and the root-mean-square deviation σ of the height of irregularities of the surface. The obtained results give the relations between Lc , Ls , and σ at which illuminating radiation behaves as monochromatic, quasi-monochromatic or polychromatic radiation and the scattered field behaves as coherent, partially coherent or incoherent field.