Path-length-resolved dynamic light scattering in highly scattering random media: The transition to diffusing wave spectroscopy

We used low coherence interferometry to measure Brownian motion within high ly scattering random media. A coherence gate was applied to resolve the opt ical path-length distribution and to separate ballistic from diffusive ligh t. Our experimental analysis provides details on the transition from single scattering to light diffusion and its dependence on the system parameters. We found that the transition to the light diffusion regime occurs at short er path lengths for media with higher scattering anisotropy or for larger n umerical aperture of the focusing optics. [S1063-651X(98)11112-1].