Independent differential depolarization parameters and their physical interpretations

Abstract

Searching for independent polarization parameters and understanding their physical meanings are important for quantifying anisotropic structures of biological tissues. In this work, six equivalent independent elementary depolarization parameters are proposed for better quantifying depolarization phenomena generated by the spatial fluctuations of birefringence and diattenuation. When the thickness of the sample is much larger than the spatial correlation lengths of the fluctuations of the six elementary polarization properties, the autocorrelation effects are the main sources of the depolarizing properties of the anisotropic media. In general, the three phase depolarization parameters may be the main off-diagonal depolarization parameters for media with fluctuations of either the birefringence or diattenuation and the presence of the amplitude depolarization can be used as indicators that in these media the spatial correlations of all the six elementary polarization parameters cannot be neglected. In addition, these results demonstrate that for a choice of the x/y and ± 45° axis directions the presence of one type of differential depolarization effects in one direction is exactly due to the existence of the spatial correlations between fluctuations of other two types of elementary differential polarization parameters along other directions.