Methodological analysis for the electrooptic coefficient and birefringence of BaTiO3 crystal films with complementary polarization modulations

Abstract

Abstract BaTiO3 crystal films, possessing advanced electrooptic (EO) properties, have spurred a broad interest in research and development of EO modulators for fiber-optic communications. However, the EO coefficient is still at uncontrollable and unoriented states despite it playing a crucial role in developing applicable industrial devices. In this work, accurate measurements of the EO coefficient r 51 and birefringence b e o of BaTiO3 crystal films are implemented with a theorem-based theoretical model, an embedded waveguide/electrode device configuration and a complementary modulation of both the linear and ellipse polarizations. Then, with two state-of-the-art device samples on different crystal films, the final average values of the r 51 and b e o are 410 ± 8 pm V−1 and −0.0208 ± 0.0003 for Sample-1 and 624 ± 31 pm V−1 and −0.0138 ± 0.0015 for Sample-2, respectively. Furthermore, a theoretical model for analyzing the measurement accuracies of r 51 and b e o is proposed and the accuracy dependences on the two key variables, drive voltage and optic–electric interaction efficiency, are investigated. Finally, the limitations to the measurement accuracy of this methodology are discussed, including the effect of temperature on the measurement accuracy of r 51 .