Electro-optical and optical evaluation of Pb(Zr, Ti)O₃ thin films using waveguide refractometry

Prism-coupled, waveguide refractometry was utilized to independently monitor electric-field-induced changes in the extraordinary and ordinary refractive indices of a Pb(Zr_0.53Ti_0.47)O₃ (PZT 53/47) thin film. Under an electric field, applied normal to the film plane and corresponding to saturation of the electric polarization, the ratio of the extraordinary to ordinary refractive index change, Δn_e/Δn_o, is found to be -4/1, contributing to a net birefringence change, Δ(n_e - n_o), of -0.021. The technique thus accesses both diagonal and off-diagonal elements of the electro-optic response tensor describing the macroscopic behavior of the polycrystalline film. In addition, the widths of the waveguide mode reflectivity minima were sensitive to variation in the microstructure of several PZT (40/60) films indicating that the refractometry technique can provide information helpful in evaluating the optical quality in these films.