Optical properties of epitaxial and polycrystalline Sr_1.8Ca_0.2NaNb₅O₁₅thin-film waveguides grown by pulsed laser deposition

Epitaxial and polycrystalline ferroelectric Sr1.8Ca0.2NaNb5O15thin films have been prepared by pulsed laser deposition on (100)MgO and fused quartz substrates, respectively. These films exhibit excellent surface flatness and high optical transmittance of about 80% over the whole visible region. Their good optical waveguide characteristics are demonstrated using prism coupling technique. Our results show that the internal scattering of the film is more influential in governing the propagation loss than the surface scattering, and that a heteroepitaxial growth of ferroelectric oxide films is essential for waveguide devices.