Method for determining the optical constants of films on absorbing substrates

We present a method to determine the optical constants (refractive indices and absorption coefficients) of films on substrates with absorption properties. The method is based on correction of the optical spectra of the films on the substrates by considering the absorption effect of the substrate. The spectra obtained after the correction are free from the influence of the absorption and can be analyzed by known methods for nonabsorbing films on nonabsorbing substrates. To illustrate the proposed method, an analysis of the spectra of CaY2F8 optical films was performed, and their optical constants were determined in the spectral range of 1.4-25 mu m. (C) 2018 Optical Society of America