Experimental study of thickness dependence of polarization and depolarization properties of anisotropic turbid media using Mueller matrix polarimetry and differential decomposition

We investigate the influence of sample thickness on the polarization and depolarization properties of light when it propagates through anisotropic turbid media using transmission Mueller matrix polarimetry. Since depolarization originates from light that has been multiply-scattered inside the sample, measurements were done by a polarimetric scatterometer equipped with large aperture optics to efficiently capture direct and scattered light. We made measurements in both, real and Fourier planes to study the distribution of polarization across the surface as well as their angular distribution respectively. We show that when properly averaged, the information obtained from images in both planes is equivalent. Rough stretched plastic sheets are used as model samples representing anisotropic turbid media which show both retardance and depolarization. The plastic sheets were stacked in different orientations to create different distributions of form birefringence, which in turn gave rise to different polarimetric properties such as linear (0°–90°, 45°–135°) and circular birefringence. We show that the dependency on the values of both, polarization properties and depolarization follows the theory of the fluctuating medium model, formulated in the framework of the differential Mueller matrix formalism. These results are used as a validation of the polarimetric scatterometer, and also, to show the interest of transmission Mueller matrix polarimetry to characterize samples showing scattering, which can be typically found in biomedicine and materials sciences.