Analytical method for the identification of a thin-strip defect in a planar waveguide

Nondestructive reconstruction of the location and width of a thin-strip defect in a strongly confined planar waveguide is considered. Explicit reconstruction formulas are given for a quick reconstruction of a thin-strip defect whose width is small by measuring the scattered fields at the two end faces of the planar waveguide for two frequencies. Numerical results are given, and the analytical reconstruction method is shown to be reliable regardless of the location of the defect.