Effect of long-scale roughness in light scattering from slightly rough dielectric layers

An experiment was conducted to demonstrate that the long-scale component of the roughness spectrum (LSR) is responsible for determining the ring positions and their dependence on incidence and scattering angle, even though the presence of the interference rings is made possible mostly by the light scattered by the small-scale roughness (SSR). The experiment used 2-mm diameter beams from an He-Ne and/or argon-ion laser, and microscope cover-glass plates and Fabry-Perot plates. The measured scattered distribution were compared with those calculated in the first Born approximation. Good quantitative agreement was found with the measurements of the scattered intensity from the slightly rough Fabry-Perot plates.