Physically admissible parameterization for differential Mueller matrix of uniform media.

In this Letter, we address the question of physical validity of differential Mueller matrix. A parameterization of entries of this differential matrix is proposed. It ensures that the generators associated with depolarization terms lead to physical Mueller matrices as for the nondepolarizing terms. A general expression for the depolarizing part of the differential matrix is found and a way to compute the nonlinear relations between the parameters is proposed.