LOW-COHERENCE INTERFEROMETRY OF PARTICLES DISTRIBUTED IN A DIELECTRICMEDIUM

Low-coherence interferometry is used to measure changes in signal inte nsity that are dependent on the phase of the light backscattered fi om particles distributed in dielectric matrices. The measurements provid e the unique opportunity to follow the dynamics of the small fraction of scattered light, to 10(-10) of the initial intensity, that retains phase characteristics of the incident wave packet. The wave phase effe cts are manifested in the observed reshaping of backscattered wave pac kets, the optical-length-dependent degree of phase randomization, and the fluctuation patterns. The experimental results indicate the presen ce of photon trapping effects. The corresponding data analysis not onl y allows for an estimation of particle concentration but also provides information on Brownian motion of particles in a liquid and character istics of par-tide distribution in size and space. (C) 1997 Optical So ciety of America.