LIGHT-SCATTERING FROM MULTILAYER OPTICS .1. TOOLS OF INVESTIGATION

We emphasize the role of correlated isotropy in the study of microroug hness in high-quality optical coatings. First, cross correlation betwe en surfaces and cross coherence between scattering sources are discuss ed and compared. An isotropy degree of roughness is then introduced as a quantitative value to describe the angular disorder of a surface co nnected with the polar dependence of scattering. We show how the frequ ency variations of this isotropy degree allow one to solve the inverse problem and obtain a unique solution for the scattering parameters th at describe structural irregularities of the stacks. Light scattering can also be used to detect an oblique growth of the materials in thin- film form. Finally, we study the sensitivity of the investigation meth od to the stack parameters.