Field distributions in the crossover from ballistic to diffusive wave propagation

Wa have measured the probability distributions of a microwave field transmitted through a random medium in the crossover from ballistic to diffusive propagation. The joint distribution of in-phase and out-of-phase components of the field is nearly Gaussian, even in samples with thickness less than the scattering mean free path. In these samples, the phase distribution of the residual held, which is the difference between the field and its ensemble average. is nearly flat. The extent of the deviation of the residual field from complete randomization depends upon the frequency, sample length, and modes of excitation.