Polarimetric scattering analysis using a Brillouin–Wigner perturbative scheme

This work presents a Brillouin-Wigner-type perturbative scheme (P-S) for deriving analytical expressions for the eigenvalues and eigenvectors of the coherence matrix, enabling computationally efficient polarimetric scattering analysis. The scheme's generality allows its application with any scattering models that verify reciprocity. As an example, it is applied using the second-order small perturbation method (SPM) for both single rough surfaces and layered media. Comparison of P-S results with direct numerical calculations of the coherence matrix demonstrates high accuracy across all studied parameters, with relative mean errors ranging from 0.2% to 7%.