Structural and optical characterization of epitaxial waveguiding BaTiO3 thin films on MgO

Epitaxial waveguide structures of $c$ -axis oriented ${\mathrm{BaTiO}}_{\mathrm{3}}$ thin films on MgO(001) have been grown by pulsed laser deposition. The structural properties of the samples have been characterized by Rutherford backscattering spectrometry/ion channeling (RBS/C), x-ray diffraction, and atomic force microscopy. We found excellent crystalline quality even up to thicknesses of a few microns. This has been confirmed by RBS/C minimum yield values of 2%–3%, a full width at half maximum of 0.36° of the ${\mathrm{BaTiO}}_{\mathrm{3}}$ (002) rocking curve, and a rms roughness of 1.1 nm for a 950 nm ${\mathrm{BaTiO}}_{\mathrm{3}}$ film. The out-of-plane refractive index was measured to be close to the extraordinary bulk value with the birefringence being about one third of the bulk value. Waveguide losses of 2.9 dB/cm have been demonstrated.