Two light beams scattering from a random rough surface by Kirchhoff theory

In this paper, a two beam Kirchhoff approach is introduced to derive the analytical expressions for coherent and diffuse scattering intensities from rough surfaces. At first, it seems the field is the sum of both the scattering beams, but the results show that for some angles, considerable deviation from the sum of two beams diffuse scattered intensity takes place which is due to the interference effect of the diffuse fields. Our calculations show that the interference of the scattered beams in both coherent and diffuse fields includes terms containing the statistical properties of the surface. We also show in which parameters it can be observed in experiments. In addition, variations of the coherent and diffuse field intensities with respect to statistical parameters of the surface, incident wave properties, incident and scattered angles are considered.