Abstract

Often, materials such as TiO₂ in thin-film form produced by classical evaporation exhibit columnar microstructure. An anisotropy of the refractive index is associated with this structural anisotropy. To describe the behavior of an optical wave propagating in the layer, one can choose a biaxal model, taking one of the three principal refractive indices (n₁, n₂, n₃) in the direction of the main axis of the columns (n₃). With such a model it is easy to write down the equations of propagation of an optical wave in a principal plane of the material [plane (n₁, n₃)]. Then we can study the propagation of the guided modes. From this study in the plane (n₁, n₃) of a single layer of TiO₂, we obtain the refractive indices n₁, n₂, and n₃ and the mechanical thickness. We have developed the formalism given by Teitler to calculate the eight reflexion and transmission coefficients in polarized light (R_SS,R_PP, R_SP, R_PS, T_SS, T_PP, T_SP, T_PS) in a plane of incidence that is rotated at an angle Φ from the principal plane (n₁, n₃) of the layer (the plane of the columns). We find that the coefficients R_SP, R_PS, T_SP, and T_PS, corresponding to a rotation of the polarization, are modulated with Φ. We have performed a comparison between the measurements and the calculated values of T_SP and T_PS. The agreement is very good when we use in our calculations the refractive indices n₁, n₂, and n₃ that we obtained from the measurements of the guided modes in the plane (n₁, n₃).

© 1990 Optical Society of America