Investigation on the Scattering Characteristics of Gaussian Beam from Two Dimensional Dielectric Rough Surfaces Based on the Kirchhoff Approximation

The scattering characteristic of paraxial gaussian beam from two dimensional dielectric rough surfaces is studied in this paper. The modification of the Kirchhoff approximation theory for rough surface scattering by an incident gaussian beam instead of a plane wave are developed based on conventional Kirchhoff scattering theory and plane wave spectrum expansion method. The coherent and incoherent scattered intensity and cross section of two dimensional dielectric rough surfaces is derived in detail. As a application, under incidence wave length λ = 1.06μm, we calculate the coherent and incoherent scattered intensity and cross section of Gaussian beam scattering from plating aluminium dielectric rough surfaces change with the scattering zenith angles in different rough surface correlation length, rough surface height root mean square and other conditions. In the same scattering conditions, we compare the coherent and incoherent scattered section between the gaussian beam and plane wave to prove that our methods and programming cods is correct. The numerical results are shown 224 Wang, Wu, and Li that the incident gaussian beam size is much larger compared with the surface height correlation length, the normalized scattering cross section is the same as for an incident plane wave. The ratio between the beam size and the surface height correlation length play an important role in the scattering characteristic of the gaussian beam from two dimensional dielectric rough surfaces. The ratio is bigger, the coherent and scattered intensity and section is more remarkable and on the contrary the incoherent scattered intensity and section is relatively smaller.