Optical description of an interface

摘要

The refractive index is the parameter used to describe the physical medium through which light propagates. It is considered that for homogeneous and isotropic materials it has a unique value at any point; hence a material border is represented by a step index function. This description assumes that the physical properties of the material at the surface are the same as those of the bulk. From the physics of surfaces we know that in the case of a solid, the interaction between the atoms (or molecules) of the solid and its surroundings are responsible of processes such as adsorption, desorption, etc. In this work we present two basic models that can be used to characterize, in terms of gradient index profiles, the physical properties of the interface. These models were developed within the physical chemistry of solids to describe the interfacial state, and we have translated them to refractive index profiles following recent results reported for optical wave-guides. The ray tracing equations obtained for light traveling through such refractive index profiles predict Goos-Hanchen effect and satisfy the reflection laws.