Study of optoelectronic devices using epitaxial barium titanate thin films grown by RF magnetron sputtering

Barium titanate in crystalline form presents ferroelectricity and a variety of significant effects. Its large piezoelectric, pyroelectric, electrooptic and photoelastic coefficients as well as its high dielectric constant make BaTiO{dollar}sb3{dollar} (BTO) an excellent choice for transducers, sensors, and optoelectronic devices. Essential to the development of such devices on a microscale basis are to prepare films of high quality, similar to those of bulk crystals, and also to develop a proper fabrication process for low-loss waveguides that allow two-dimensional confinement of light.; In this thesis we have studied the deposition of epitaxial BaTiO{dollar}sb3{dollar} films on MgO single crystal substrates using an RF magnetron sputtering technique. The BaTiO{dollar}sb3{dollar} films were found to have a single crystal structure with an in-plane epitaxial relationship of BTO (100) {dollar}parallel{dollar}MgO (100) as confirmed by X-ray diffraction pole figure measurement. BaTiO{dollar}sb3{dollar} films' electrical, optical, and structural properties were studied and compared to those of the bulk material. Erbium-doped epitaxial BaTiO{dollar}sb3{dollar} thin films were also developed using RF magnetron sputtering. The Er-doped BaTiO{dollar}sb3{dollar} films show clear room temperature photoluminescence at 1.54 {dollar}mu{dollar}m which corresponds to {dollar}rmsp4Isb{lcub}13/2{rcub}to{lcub}sp4I{rcub}sb{lcub}15/2{rcub}{dollar} transitions of Er{dollar}sp{lcub}3+{rcub}{dollar} ions. This new, added, property may be useful for the design of a new generation of guided optic devices presenting optical gain.; We have also developed a novel method for forming channel waveguides in BaTiO{dollar}sb3{dollar} films. The method exploits the photoelastic effect of BTO induced by thin-film stress. We have carried out numerical analyses on the stress distribution by solving the coupled equations that describe the elastomechanical and piezoelectric effects in the ferroelectric material. The refractive index changes were then calculated taking into account both the photoelastic and electrooptic effect of BaTiO{dollar}sb3.{dollar} The simulation result shows a good agreement with the measurement result. The waveguide structure developed in this thesis does not require etching of BTO, and is expected to be useful as a simple and economical method for forming channel waveguides with other ferroelectric films as well. Electrooptic intensity modulators were also developed using the BTO channel waveguides. Electrooptic modulation of light was demonstrated and the corresponding electrooptic coefficient of our BaTiO{dollar}sb3{dollar} films was extracted from the experimental data.