Hetero-Epitaxial Structures of Litao3 Thin Films

AbstractWe have grown epitaxial thin films of LiTaO3 on various substrates. LiTaO3 grows epitaxially on (111) GaAs and forms a waveguide with its underlying buffer layer of MgO, providing a desirable structure for monolithic integration. LiTaO3 grows on LiNbO3 with a buffer layer of magnesium niobate or magnesium tantalate to form an optical waveguide structure having good lattice matching and pronounced differences in refractive index. This heterostructure has the potential for reducing crystal imperfection of waveguides and improving optical confinement. We also describe a multilayer structure using an epitaxial conducting layer as a bottom electrode to grow a nonlinear optical waveguide on LiNbO3 for waveguide switching and modulation. Both light-absorbing metals and transparent metallic oxides are employed. Ion channeling and x-ray diffraction reveal high crystalline quality of the hetero-epitaxial structures. The influence of surface polarity, thermal expansion, and lattice matching on waveguiding LiTaO3 thin films is addressed.