Representation of the transparent layer-arbitrary substrate system parameters through the Fourier coefficients of the ellipsometric function

A system of transparent layers on top of an arbitrary underlying subsystem is considered. It is shown that the layer refractive index and the subsyste m generalized Fresnel coefficients can be expressed in a simple and explici t way by the Fourier coefficients of the ellipsometric function rho with th e layer thickness as an expansion parameter. Thus the inverse ellipsometric problem is reduced to a much simpler and well-defined problem of finding t hese Fourier coefficients. Analysis shows that the ellipsometric inverse ta sk must be considered separately, depending on whether the modulus of the s -polarization Fresnel coefficient for the ambient-layer interface is smalle r than, equal to, or greater than that for the layer-substrate system. (C) 1999 Optical Society of America [S0740-3232(99)00602-X].