Preparation and characteristics of seeded epitaxial (Sr,Ba)Nb2O6 optical waveguide thin films using sol-gel method

Highly c-axis-oriented (Sr,Ba)Nb2O6 (SBN) films were grown on a seeded MgO( 100) substrate via sol-gel method. The substrate was preseeded with epitaxi al islands of SBN made by breaking up a continuous film into single-crystal islands by pores. Since the number of epitaxial nuclei was increased at th e interface between the film and the substrate, the film on a seeded substr ate had better highly orientation than that on unseeded substrate. The film having low Sr content exhibited better epitaxial growth because of the dis torted unit-cell network and the change of lattice parameters of SBN thin f ilm. For obtaining excellent optical properties, SBN:75 film was prepared o n MgO substrate with SBN:25 composition seed layer. Because of low birefrin gence of refractive indices in the film having high Sr content, the optical scattering loss by the anisotropy of refractive indices was suppressed.