Comparative study of optical activity in chiral biological media by polar decomposition and differential Mueller matrices analysis

The introduction of polarimetry in optical imaging of biological tissues provides a powerful method to enhance contrast and specificity in the characterization of anisotropic biological tissues. Moreover, the fact that Mueller calculus can deal with partially polarized light and depolarizing media enables to analyze the strong effect of scattering in light propagation through biological tissues. The inherent heterogeneity of biological tissues causes that multiple effects are overlapped in a single measurement. Regarding polarimetry, anisotropic structures can simultaneously exhibit birefringence, diattenuation and depolarization. Lu-Chipman polar decomposition has been widely used in order to isolate the effects and quantify each of them. However, it entails a limitation: as long as the original Mueller matrix is decomposed into the product of three components, the result of the decomposition varies with the order. In this work, we propose a polarimetric analysis based on differential Mueller matrices. This analysis is not affected by the order in which the effects take place within the medium. We apply it to the study of optical activity in chiral and turbid biological media, in particular to a solution of glucose mixed with an aqueous suspension of polystyrene microspheres. The results obtained by Lu-Chipman polar decomposition and by differential Mueller matrices analysis are compared. It will be shown that the results obtained by the polarimetric analysis proposed in this work are in good agreement with those obtained by polar decomposition, with the advantage that differential Mueller matrices provide additional information to further develop polarimetric analysis in a robust way