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Understanding light propagation in fibrous tissue plays a fundamental role in the development of novel and minimally invasive diagnosis techniques. For this purpose, we have developed a polarimetric microscope that operates in the backscattering geometry. Our apparatus has been thoroughly calibrated and verified with
experiments and Monte Carlo simulations on well characterized colloidal suspensions. In this study, we have investigated the feasibility of retrieving structural information on multiply scattering, fibrous electrospun scaffolds fabricated of Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDFhfp) nanofibers having diameters ranging from 500 to 1000 nm. These nanofibers display various degrees of structural alignment and the structural anisotropy manifests itself in optical birefringence. We probed these scaffolds with a focused near-infrared light beam at three pairs of cross-polarized states and recorded images of the Stokes vector elements of the light backscattered at the surfaces of the scaffolds. Our results demonstrate that it is possible to structurally differentiate the scaffolds by analyzing the spatial variations of the Stokes vectors/polarization ellipses as a function of the polarization state of the probing beam. Visualizing the rate of retardance induced by the birefringent fibers together with the distribution of the degree of polarization unveils the orientation of these fibers and their respective degree of organization, which was compared to results obtained by small angle x-ray scattering (SAXS). This study contributes to a better understanding of the interaction of the light with multiply scattering fibrous matter such as tissue, which is particularly challenging in the backscattering geometry but fundamental to make the diagnosis of cancer possible.
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