Frustrated Total Reflection and Its Application to the Measurement of the Refractive Index and Thickness of Thin Transparent Films

Abstract

A comprehensive review is made of the literature on total reflection. The expressions for the transmission through thin films in conditions of frustrated total reflection are derived. These formulae are applied to the solution of the optical constants of thin transparent films and the method is used to measure the refractive index and thickness of thermally evaporated magnesium fluoride films. Polarimetric and multiple beam interference methods are used to check the results. The method of using frustrated total reflection for the measurement of the optical constants of thin films appears to be as accurate as other methods. There is some indication to suggest that theories based on the concept of plane, parallel-sided, homogeneous and isotropic films are insufficient for the problems associated with thermally evaporated thin films.