Electrooptic Effect in Ti:doped LiNbO3 Thick Films Grown by Sol-Gel Method

Stoichiometric LiNbO₃ thick films on a z-cut LiNbO₃ substrate were grown by using a sol-gel method improved by the addition of a large amount of protective colloid such as polyvinyl alcohol to the precursor solution. This method has been expanded to grow Ti-doped LiNbO₃ waveguide films and low propagation loss and efficient electro-optic effect for these films have been made clear using a Mach-Zehnder interferometer. The magnitude of Pockels effect in the waveguide structure has been compared with that of a z-cut congruent LiNbO₃ substrate and the similar results have been confirmed. The superiority of this epitaxial layer to the previous one that enables us to fabricate with easy processing and low cost is also discussed.