Experimental investigation of circular light depolarization using polarization sensitive OCT

We present an experimental study of the depolarization of circularly polarized (CP) light backscattered from random media. We employ a polarization sensitive OCT, capable of producing intensity profiles for two orthogonal polarization channels simultaneously. For CP light backscattered from polystyrene solutions containing spherical particles of sizes larger than the radiation wavelength, the phenomenon of polarization memory is observed. The degree of circular polarization (DOCP) as a function of the path the light travels in the medium depends on the scatterers' size. In the case of scatterers larger than the wavelength, the DOCP exhibits a minimum indicating a helicity cross-over. The copolarized light then exceeds the intensity of cross-polarized light of backscattered radiation, a phenomenon predicted theoretically but not observed experimentally so far. The helicity cross-over is observed in the DOCP curves for large scatterers at small and large concentrations.