Propagation of electromagnetic waves through inhomogeneous slabs

An approximation technique is considered for computing transmission and reflection coefficients for plane waves propagating through stratified slabs. The approximation uses a mapping of the given problem onto a similar, but exactly solvable problem. The approximate solution is then expressed in terms of the solution of the exactly solvable problem. As an illustration of the technique, the reflection and transmission coefficients of a transition layer are computed. Agreement between the exact and approximate values of the coefficients is good.