Electromagnetic diffraction at thick curved inhomogeneous layers

This paper considers the original asymptotic method for the analysis of electromagnetic diffraction at electrically thick dielectric layers. The approach is based on combining the small-parameter expansions of the field inside the layer and the raytracing outside of the layer. The first two terms of asymptotic expansion are derived. The first term already comprises the correction on layer's curvature. The method is validated and verified by comparison with the corresponding results of solving the Muller boundary integral equation. The limitations of the plane-slab approximation of the curved layer are also discussed.