Polychromatic reflectance and transmittance of a slab with a randomly rough boundary

We investigated four different approximation models for describing the poly chromatic reflectance and transmittance of a slab with a randomly rough bou ndary while taking into account the coherent and the incoherent scattering of the rough boundary. Comparisons with experiments (an etched-silicon wafe r) show that approximation models that apply a two-scale roughness to the r andomly rough boundary and that take into account the coherent and the inco herent scattering yield better agreement and extend the range of validity o f the approximation to shorter wavelengths. (C) 1999 Optical Society of Ame rica.