Time-resolved studies of light scattering in random media

Abstract

Angle- and time-resolved studies of the ultrashort pulses propagating through a slab of random media with a few transport mean free paths thick reveal that a coherent component coexists with an incoherent component in the forward direction. The coherent component behaves as an unscattered pulse propagating in the forward direction, whereas the incoherent part experiences multiple scatterings and exhibits a diffusive characteristic. In the intensity temporal profile of the scattered pulse in the forward direction, the peak intensity of the diffusive pulse displaces farther away from the ballistic pulse when the size of the scatterers decreases or the thickness of the random media increases. The smaller scatterers and thick medium also show a much larger distribution of arrival times. The theoretical results from the two-frequency coherent function in the Rytov approximation are in qualitative but not in quantitative agreement with the experimental results. The depolarization of light in the backward direction shows a significant dependence on the size and concentration of the scatterers. The parallel polarized backscattered pulse profile is significantly broader than its perpendicular counterpart in media with a particle size smaller than the wavelength of light.