Speckle statistics of doubly scattered light

The statistical properties of light that has been scattered twice are studied in theory. If each scattering by itself gives rise to Gaussian speckle, it is found that the probability densities of the doubly scattered light amplitude and intensity are approximately K distributions, which imply stronger fluctuations than Gaussian light. The spatial-correlation properties of the doubly scattered light are also examined. The intensity correlations contain non-Gaussian terms, and, although the correlations are spatially stationary, they indicate that the doubly scattered light is not an ergodic process.