Isotropic Optical Properties of Epitaxial PLZT Thin Films

Epitaxial (Pb 1-x , La x )(Zr 1-y , Ti y ) 1-x/4 O 3 [PLZT] films composition dependence of the refractive index and electric-optic (EO) coefficient near the morphotropic phase boundary (MPB) composition was investigated. A (100/001)-oriented PLZT 9/65/35 epitaxial film is found to have isotropic optical properties. Highly (100/001)-oriented epitaxial PLZT films with compositions near the MPB on Nb-SrTiO 3 substrates were fabricated using a sol-gel process. The refractive index decreases with increasing lanthanum content. The difference in the refractive index obtained depended upon the lanthanum content up to 2 %. This value is adequate for fabrication of waveguide structures. The value of birefringence from 4×10 -3 to 5×10 -4 in PLZT epitaxial film was smaller than that of lithium niobate single crystal. The EO coefficient of PLZT 9/65/35 thin films was 45 pm/V, which is larger than that of lithium niobate single crystal. A very small polarization dependence of the EO coefficient was also observed.