Diffusion of Classical Waves in Random Media

Abstract

In recent years there has been growing interest in studies of the propagation of classical waves in random media.1,2 The revival of interest in the longstanding problem of multiple scattering of classical waves was initiated by the discovery of the importance of quantum interference effects for the transport properties of electrons in disordered systems.3 While some of the features associated with electron localization, such as enhanced coherent backscattering, have been detected in light scattering experiments4 as well, the localization of electromagnetic waves or other classical waves in random systems has not been established beyond doubt. The question of localization of classical waves has attracted attention for two reasons. First, the properties of classical waves such as light waves, microwaves, and acoustic waves in random media are of fundamental interest for their own sake. Second, classical waves can serve as a model system for testing the theory of Anderson localization of electrons experimentally in a clean way, without the complication of strong inelastic scattering and other effects of electron-electron and electron-phonon interaction. On the other hand, it is harder to localize classical waves, mainly due to the fact that at low frequency the effect of disorder tends to average out in this case, whereas electrons at low energy are trapped more effectively, even by a weak random potential.