A uniform approximation to the scattering and propagation problem for a stratified bi-anisotropic slab

The scattering and propagation problem for time-harmonic waves in a stratified bi-anisotropic slab is considered. Based upon the identification of the left- and right-moving modes, and on a boundedness assumption concerning the space and frequency dependence of the physical parameters, a sequence of approximate solutions which converge absolutely and uniformly to the exact solution are derived. In particular, if the magnetoelectric coupling is small and the permittivity and permeability vary slowly, the approxi mate solutions converge so fast that the first approximation already gives a satisfactory approximation. With the present approximation method, approximate solutions valid for all frequencies can be obtained in explicit form.