Graphical method to design internal reflection phase retarders

Abstract

Total internal reflection (TIR) results when light is reflected from a rare-to-dense interface between two dielectric media at an angle that exceeds the critical angle. The phase retardance, which is the difference between the TIR phase changes for the two planes of polarization, is a function of the refractive indices of the media and the incident angle. The addition of a transparent thin-film multilayer coating may be used to change the phase retardance of the interface to a value appropriate for a specific application. A graph of phase retardance D vs the average phase shift A as a function of layer thickness provides a means for visualization that is useful in the design process. The D–A graph predicts the phase properties of a coated TIR interface as a function of index and thickness of an added layer. Graphs of phase retardance vs average phase change for two or more different materials may be superposed to predict the phase performance of a multilayer coating. This graphical technique is employed to analyze and design several coatings.