Intensity angular correlations of light multiply scattered from random rough surfaces

Abstract

The intensity angular correlation function in multiple scattering of electromagnetic waves from randomly rough one-dimensional interfaces that separate a vacuum from a perfect conductor is studied by numerically solving the scattering equations that are based on the extinction theorem boundary condition. The so-called memory effect, discussed elsewhere for dense random media, is encountered, and its angular width is found to be considerably larger than for volume scattering. Comparisons are also made with situations for which the Kirchhoff approximation holds. In addition, because of the small number of asperities of the surface samples dealt with in the computations, a new enhanced long-range correlation of width reciprocal to the mean free path is found as a result of constructive interference between waves whose wave vector is the sum or difference of initial and final wave vectors and wave vectors that are due to time-reversed paths. The origin of this correlation effect, in that it is due to multiple scattering, is analogous to that of the peak of enhanced backscattering for the mean scattered intensity and arises from the non-Gaussian second-order statistics of the scattered field.