Structure of polarimetric purity of a Mueller matrix and sources of depolarization

The depolarization properties of a medium with associated Mueller matrix M are characterized through two complementary sets of parameters, namely the three indices of polarimetric purity (IPP), which are directly linked to the relative weights of the spectral components of M and provide complete information on the structure of polarimetric randomness, but are insensitive to the specific polarimetric behaviors that originate the lack of randomness; and the set of three components of purity (CP), constituted by the polarizance, the diattenuation and the degree of spherical purity. The relations between these sets of physical invariant quantities are studied by means of their representation into a common purity figure. Furthermore, the polarimetric properties of a general Mueller matrix are parameterized in terms of sixteen meaningful quantities, three of them being the IPP, which together the CP provide complete information of the amount and sources of depolarization of the medium to which M is associated.