Circular polarized incident light scattering properties at optical clearing in tissues

This paper focuses on polarization imaging during optical clearing process in tissues due to refractive index matching of tissue structural components. We start with some single-dispersed tissue models, composed of large spheres, small spheres, and large cylinders, respectively. Along with the simulated refractive index matching inside and outside the scatterers, the linear polarized incident photons show similar decreased depolarization. It is worth noting that the circular polarized incident light show different polarization change for different scatterers, sensitive to scatterer size and shape. For small Rayleigh-like spherical scatterers, the circular depolarization also decreases with index matching. However, the depolarization by the larger scatterers can be enhanced, supported by the photon distribution change with the index matching in the backward detection. After some extreme points, the depolarization of circular polarized photons will be suppressed until almost disappear. Furthermore, by the simulation of hybrid-dispersed models, we can find out that the transmission of circular polarized photons during optical clearing, is more sensitive to the content of smaller scatterers in the turbid medium, and also has a close relationship with the proportion of the anisotropic scatterers. We also extract a character to describe the difference of linear and circular polarized photons. The value and the change of this character can help us to explain the main scatterers contributed to the polarization features of tissue-like medium during optical clearing. The above results indicate different polarization features for different scattering systems by optical clearing, which are potentially useful for studying optical clearing by polarization methods.