The polarimetric properties of a material medium are summarized in the sixteen elements of its associated Mueller matrix. The quantities carrying specific information on the significant polarimetric features have to be defined on the basis of the analysis of the mathematical structure of Mueller matrices. It is found that any Mueller matrix can be parameterized through two retardance vectors and ten quantities that are invariant under dual retarder transformations. This parameterization leads to proper definitions of the retardance and depolarization properties, which together with the diattenuation and polarizance properties provide complete polarimetric characterization of the sample under consideration.
José J. Gil, José J. Gil,
"Physical quantities involved in a Mueller matrix", Proc. SPIE 9853, Polarization: Measurement, Analysis, and Remote Sensing XII, 985302 (4 May 2016); doi: 10.1117/12.2222758; https://doi.org/10.1117/12.2222758