Path-length-resolved dynamic light scattering: modeling the transition from single to diffusive scattering

Dynamic light-scattering spectroscopy is used to study Brownian motion with in highly scattering samples. The fluctuations of the light field that is b ackscattered by a suspension of polystyrene microspheres are measured as po wer spectra by use of low-coherence interferometry to obtain path-length re solution. The data are modeled as the sum of contributions to the detected light weighted by a Poisson probability for the number of events that each component has experienced. By analyzing the broadening of the power spectra as a function of the path length for various sizes of particles, we determ ine the contribution of multiple scattering to the detected signal as a fun ction of scattering anisotropy. (C) 2001 Optical Society of America.