Processing thin films of KNbO3 for optical waveguides

Thin film waveguides of ferroelectric materials hold great promise for use in active integrated optics devices because of the high optical confinement possible in a thin film structure. KNbO 3 is an attractive material for active devices because it possesses large nonlinear optical susceptibilities and large electro-optic coefficients. KNbO 3 films with low optical losses are required to produce efficient devices. Epitaxial films of KNbO 3 (110) have previously been deposited on single crystal MgO (100) using ion beam sputtering techniques. However, these films contained microstructural defects due to the large lattice mismatch (>4.0%) between KNbO 3 and MgO which resulted in high optical losses. Recent work has focused on determining the relationships between microstructure and optical loss through the use of lattice matched substrates. Film composition, epitaxial quality and optical properties of KNbO 3 films deposited on MgO and MgAl 2 O 4 have been investigated and are compared.