Polarimetric optical theorem

The classical optical theorem that describes the extinction of electromagnetic radiation by an arbitrary particle is reformulated by use of the diffusion properties of the mutual spectral densities. This reformulation yields three novel coherency tensors: an extinction-loss coherency tensor, a scattering-loss coherency tensor, and an absorption-loss coherency tensor. The first tensor is used to establish the polarimetric optical theorem and to derive the extinction-loss matrix. The second tensor is used to derive the scattering-loss matrix. The third tensor is used to develop the absorption-loss matrix and the absorption cross sections. Furthermore, the derived extinction- and scattering-loss matrices are found to be similar to the extinction coefficient and phase matrices of the vector radiative transfer equations.