Transition from Ballistic to Diffusive Behavior for Multiply Scattered Waves

Abstract

Wave propagation in random media has been the focus of considerable attention in the past decade [1,2]. Various interesting wave phenomena have been uncovered, and studied, e.g., the coherent backscattering effect[3], short-range and long-range spatial intensity correlations [4,5], and dynamical intensity correlations [6], etc. In case when the sample size is much greater than transport mean free path, great simplification in theoretical treatments has been found in the diffusion approximation. The diffusion approach has been successful in describing most of the phenomena observed, including the coherent backscattering cone and its sample size dependence [7], and the spatial intensity correlations [8,9], etc. It works well even in the case when there are internal reflections in the random media [10,11]. The application to the coherent backscattering of the scalar acoustic waves is also excellent [12]. It should be noted that the diffusive property of light has recently been used to advantage as a new optical imaging technique [13].