Scattering matrix of elliptically polarized waves

we analyze the scattering of elliptically polarized plane waves normally incident at the planar interface between two different materials; we consider two cases: dielectric-dielectric and dielectric-conductor interfaces. the scattering s matrix in both cases is obtained using the boundary conditions and poynting's theorem. in the dielectric-dielectric case we write s using two different basis, the usual xy and a rotated one. for the dielectric-conductor interface, the use of the rotated basis together with an energy balance argument leads us, in a natural way, to construct a unitary s matrix after recognizing the need to introduce two equivalent parasitic channels due to dissipation in the conductor, and the transmission coefficient into these parasitic channels measures the absorption strength.