Long-range saturation of spatial decoherence in wave-field transport in random multiple-scattering media

The transverse spatial coherence of an optical beam alters as the light tra verses a dense, multiple-scattering, random dielectric medium. Results of m easurements show the predicted initial increase of the decoherence (or deco rrelation) rate with spatial separation, followed by saturation at large se paration. This behavior can be modeled by using a Boltzmann-like transport equation for the Wigner function of the wave held, whereas the standard mod el for decoherence (developed for quantum wave fields), which is based on t he Fokker-Planck phase-space diffusion equation, contains no saturation and fails at all separations to describe the observed behavior.