WAVE-GUIDE REFRACTOMETRY AS A PROBE OF THIN-FILM OPTICAL UNIFORMITY

Optical inhomogeneities through the thickness of a sol-gel-derived, sp in-coated Pb(Zr,Ti)O-3 (PZT) thin film have been evaluated using prism -coupled waveguide refractometry. Unusual waveguide coupling angle beh avior has been treated using a multilayer model to describe the optica l characteristics of the film. Waveguide refractometry measurements, p erformed after incremental reductions in film thickness, were used to develop a consistent model for optical inhomogeneity through the film thickness. Specifically, a thin film layer model, consisting of altern ating layers of high and low refractive index material, was found to a ccurately predict irregularities in transverse-electric (TE) mode coup ling angles exhibited by the film. This layer structure has a spatial periodicity that is consistent with the positions of the upper film su rface at intermediate firings during film synthesis. The correlation e mphasizes the impact of the multistep thin-film deposition approach on the optical characteristics of the resulting thin film.