Role of interface correlation in light scattering by a multiplayer

Abstract

Four industries prepared optical coatings with a common design that permits an easy determination of cross-correlation laws between the rough interfaces in the stack. Different pairs of materials and deposition processes were used. After clarifying the differences between scalar and vector theories of light scattering caused by rough interfaces in optical multilayers, we compare the experimental values with both theories. Factors such as variations of correlation with spatial frequency, residual roughness, and slight errors in the design are taken into account for comparison with the vector theory of angular scattering. Correlation of the interface roughnesses is found to be high for practically all coatings. However, at low scatter-loss levels, scattering by localized defects in the coatings appears to dominate over the scattering caused by rough interfaces.