The real and imaginary parts of the complex dielectric function (or complex refractive index) of an opaque substrate or a thick film can be determined from two pseudo-Brewster angles measured in two transparent incidence media of different refractive indices. This two-angle method is simple in that it involves no photometric or polarimetric analysis and in that the solution for the optical properties in terms of the measured angles is explicit, analytical, and direct (i.e. noniterative). The two-angle method is demonstrated for an opaque TiN film on a Cleartran ZnS substrate as a specific example. The effect of angle-of-incidence errors on the determination of the optical properties is investigated, and the domain of applicability of this new and interesting method is also delineated.
Journal of the Optical Society of America A
R. M. A. Azzam, "Analytical determination of the complex dielectric function of an absorbing medium from two angles of incidence of minimum parallel reflectance," J. Opt. Soc. Am. A 6, 1213-1216 (1989)