Stress-induced lateral confinement of light in epitaxial BaTiO3 films grown by radio-frequency magnetron sputtering

We report channel waveguides formed in epitaxial ${\mathrm{BaTiO}}_{\mathrm{3}}$ films that were grown on MgO single-crystal substrates using rf magnetron sputtering. In the channel waveguides developed, the lateral confinement of light is achieved via the photoelastic and piezoelectric/electro-optic effects in ${\mathrm{BaTiO}}_{\mathrm{3}}$ induced by thin-film stress. Numerical analyses were also carried out on the stress and piezoelectric field distributions in the channel structure, assuming bulk materials properties. The refractive index changes were then calculated taking into account both the photoelastic and electro-optic effects of ${\mathrm{BaTiO}}_{\mathrm{3}}.$ The simulation result suggests that the electro-optic effect (caused by the stress-induced piezoelectric field) accounts for a significant portion (∼10%) of the refractive index change in the channel region.