DISPERSION-RELATION FOR BIANISOTROPIC MATERIALS AND ITS SYMMETRY PROPERTIES

The dispersion relation for an arbitrary general bian-isotropic medium is derived in Cartesian coordinates, in a form well suited to imposing the boundary conditions when dealing with layered media with planar and parallel interfaces. Special cases of practical interests are also considered. Eleven fundamental coefficient families are identified by considering in detail all the symmetries present in the dispersion relation. An ad hoc expression of the determinant of the sum of two 3 x 3 matrices permits to use a simple procedure to obtain the coefficients of the dispersion equation. The symmetry properties pointed out in this work have general validity, and this technique to evaluate the coefficients may be useful also in other fields of application where dispersion relations are of importance.