THEORETICAL COMPARISON OF LIGHT-SCATTERING AND GUIDED-WAVE COUPLING IN MULTILAYER COATED OPTICAL-COMPONENTS WITH RANDOM INTERFACE ROUGHNESS

In this work, we use first-order perturbation theory to calculate and then compare the (1) angular distribution of incident light scattered from a multilayer-coated optical component and (2) the angular distrib ution of incident light coupled into guided waves supported by the mul tilayer component. The incident beam is assumed to be a monochromatic plane wave and the scattering/coupling is assumed to be caused by roug hness at the interfaces of the optical component. Numerical results sh ow that for high quality (low root mean square roughness) optical comp onents, comparison of the relative amounts of incident energy (1) scat tered out of the specular beam and (2) coupled into guided waves are c omparable. It follows that the guided wave energy will further contrib ute to the scattered field via radiative decay or be converted to heat . Thus, this work can help provide an estimation of when guided wave c oupling can occur along with the expected magnitude.