Generalized WKB Approximation for Stratified Isotropic Chiral Media

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Abstract
The WKB method and its generalization, well known to be applicable to a certain class of achiral isotropic inhomogeneous media, are extended to stratified chiral media for waves with normal incidence. The method is based on an expansion in wave fields, certain combinations of the electric and magnetic fields, whose properties are also extensively studied in the paper. It is seen that for sufficiently slowly varying media, the reflection dyadic due to the stratification can be expressed in closed integral form and, for normal incidence, the result is independent of the chirality parameter κ applied in this paper. The method can be further extended for chiral media to what is known as the Bremmer series method for achiral media.