Polarization-based optical techniques have become increasingly popular in the field of biomedical diagnosis. In the current report we exploit the directional awareness of circularly and/or elliptically polarized light backscattered from turbid tissue-like scattering media. We apply circularly and elliptically polarized laser light which illuminates the samples of interest, and a standard optical polarimeter is used to observe the polarization state of light backscattered a few millimeters away from the point of incidence. We demonstrate that the Stokes vector of backscattered light depicted on a Poincaré sphere can be used to assess a turbid tissue-like scattering medium. By tracking the Stokes vector of the detected light on the Poincaré sphere, we investigate the utility of this approach for characterization of cancerous and non-cancerous tissue samples in vitro. The obtained results are discussed in the framework of a phenomenological model and the results of a polarization tracking Monte Carlo model, developed in house. Schematic illustration of the experimental approach utilizing circularly and elliptically polarized light for probing turbid tissue-like scattering media.

Within the framework of further development of unified Monte Carlo code for the needs of biomedical optics and biophotonics, we present an approach for modeling of coherent polarized light propagation in highly scattering turbid media, such as biological tissues. The temporal coherence of light, linear and circular polarization, interference, and the helicity flip of circularly polarized light due to reflection at the medium boundary and/or backscattering events are taken into account. To achieve higher accuracy in the results and to speed up the modeling, the implementation of the code utilizes parallel computing on NVIDIA graphics processing units using Compute Unified Device Architecture. The results of the simulation of coherent linearly and circularly polarized light are presented in comparison with the results of known theoretical studies and the results of alternative modelings.

We investigate the survival of circularly polarized light in random scattering media. The surprising persistence of this form of polarization has a known dependence on the size and refractive index of scattering particles, however a general description regarding polydisperse media is lacking. Through analysis of Mie theory, we present a means of calculating the magnitude of circular polarization memory in complex media, with total generality in the distribution of particle sizes and refractive indices. Quantification of this memory effect enables an alternate pathway towards recovering particle size distribution, based on measurements of diffusing circularly polarized light.

Strong multiple scattering of light is typical for most biological tissues and leads to the loss of initial polarization, direction, phase, and wavefront of incident optical radiation. Circular polarization survives more scattering events than the direction of its propagation, whereas the helicity of backscattered optical radiation depends noticeably on the size of scattering particles. In the current study an approach of probing a disperse random medium with the use of back-scattered circular polarized light is presented. We show that the helicity flip of circular polarized light can be observed experimentally in the tissue-like media and that it is sensitive to the direction of light propagation. The flip in helicity is clearly seeing as the polarization vector traverse of the Q -U plane of the Poincaré sphere. It has been also demonstrated, for the first time in our knowledge, that the polarization changes induced by optical clearing can be clearly observed and analyzed quantitatively by tracking the polarization vectors on the Poincaré sphere.