On the Solution of an Ill-Posed Non-Linear Fredholm Integral Equation Connected with an Inverse Problem of Thin Film Optics

The identification of stratified media (for the mathematical and physical background see, e.g., [51), that means, the determination of structure parameters from indirect measurements, is the aim of many papers (see, e.g., [2]). Questions for existence, uniqueness, and stability of solutions are often not sufficiently noted although ill-posedness must taken into account solving problems of this type. Especially, we will consider these qualities of solutions for the so-called WKB-(Webster-Kramer-Brillon)-Method, which is very important for the simultaneous identification of thickness and refractive index profile for inhomogeneous thin films from photometric