Abstract

A method for determining the optical properties of a film on an isotropic substrate is proposed. The method is based on the existence of two specific incidence angles in the angular interference pattern of the p-polarized light where oscillations of the reflection coefficient cease. The first of these angles, θ_B1, is the well-known Abelès angle, i.e., the ambient–film Brewster angle, and the second angle θ_B2 is the film–substrate Brewster angle. In the conventional planar geometry and in a vacuum ambient there is a rigorous constraint ε₁ + ε > ε₁ε on the film and the substrate dielectric permittivities ε₁ and ε, respectively, for the existence of the second angle θ_B2. The limitation may be removed in an experiment by use of a cylindrical lens as an ambient with ε₀ > 1, so that both angles become observable. This, contrary to general belief, allows one to adopt the conventional Abelès method not only for films with ε₁ close to the substrate’s value ε but also for any value of ε₁. The method, when applied to a wedge-shaped film or to any film of unknown variable thickness, permits one to determine (i) the refractive index of a film on an unknown substrate, (ii) the vertical and the horizontal optical anisotropies of a film on an isotropic substrate, (iii) the weak absorption of a moderately thick film on a transparent or an absorbing isotropic substrate.

© 1999 Optical Society of America

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