Optical properties of PLZT thin films fabricated by a sol-gel method

Optical properties of epitaxial PLZT thin films with compositions near the morphotropic phase boundary were studied as the La content of the boundary was changed from 0 to 10 atom%. PLZT thin films with thickness of over 2 mum were fabricated on Nb-doped SrTiO3 (100) substrates by a sol-gel method. Highly (001) oriented epitaxial PLZT thin films were obtained. Polarization dependence of the refractive index and electric-optic (EO) coefficient was measured using a prism coupling method. The refractive index changed by up to 2% as the La content was increased. Birefringence became small from 4 x 10(-3) to 5 x 10(-4) as the La content increased and the crystal structure almost became cubic. The EO coefficient increased from 25 pm/V to 45 pm/V as a function of La content in a range of 0 to 9 atom%, but the EO coefficient decreased to 30 pm/V in films with 10 atom% La. EO coefficient of PLZT (9/65/35) thin films was higher than LiNbO3 single crystal. Polarization dependence of the EO effect was not observed in the sample.