Electromagnetic field correlations in three-dimensional speckles

We describe recent developments in the characterization of three-dimensional speckle fields produced by scattering of electromagnetic waves. In many practical situations the description of such fields requires approaches going beyond the Gaussian statistics approximation. Quantitative measures of spatial coherence and polarization can be defined from the field-field correlation matrix, known as the cross-spectral density matrix in coherence theory. The complex degree of mutual polarization provides a measure of the similarity between polarization states at two different points. The degree of spatial coherence describes spatial coherence and averages out the polarization properties. We discuss their behavior in speckle fields produced by multiple scattering in disordered materials. A number of non-universal properties arise, that are related to the internal microscopic structure of the scattering medium. Non-universality affects observables quantities, such as spatial correlations in speckle patterns measured in the near field of the medium surface, statistics of the local density of states or the depolarization of the exciting electromagnetic field due to scattering. Specific microscopic scales are necessary to describe the non-universal behaviors, that characterize the scale-dependent morphology of the scattering medium. (C) 2015 Published by Elsevier B.V.