Optical Properties of an Ionic Crystal Slab

Abstract

The theory of the optical properties of an ionic crystal slab is formulated to exhibit explicitly the relation between the optical properties and the virtual modes of the slab. It is shown that the absorption spectrum can be completely understood from the properties of the virtual modes. Expressions for the contribution of a single virtual mode to absorption, reflection, and transmission are compared with exact calculations for LiF. The total width of an absorption peak is shown to be expressible as the sum of a radiative width and a width due to lattice anharmonicities.