Propagation along the direction of inhomogeneity in an inhomogeneous chiral medium

Wave propagation in unidirectionally inhomogeneous chiral media is examined, i.e. the constitutive properties of the chiral media vary along the z axis; it is also assumed that the electromagnetic field is a function of the z coordinate alone. It is shown that the electromagnetic field, in the present arrangement, can be decomposed into two mutually-independent circularly-polarized states. Coupled first-order differential equations are derived to describe the fields, and various solution procedures discussed. Extension is made to the case when the medium inhomogeneity is periodic, for which case a perturbational solution is explicitly given.