Spectrophotometric determination of optical parameters of lithium niobate films

Lithium niobate films on silicon substrates have been synthesized by high-frequency magnetron sputtering of a target. The spectral dependences of the reflectance in the 300-700 nm range at small incidence angles and the angular dependence of p- and s-polarized light for a discrete set of wavelengths from 300 to 700 nm with wavelength increments of 50 nm, for angles of 1 arc deg, have been obtained using spectrophotometry. The refractive indicies, the film thickness and the extinction coefficients have been determined using a numerical method for solving inverse problems. The initial approximations for the solution of inverse problems have been defined using methods based on the estimation of the interference extrema positions in the reflection spectra. The resultant refractive indicies of the film differ from those typical of LiNbO3 single crystals. These differences are attributed to the structural disorder induced by the predominant crystallite orientation and the absorption in the film.