Nonlinear properties of LiNbO3/Al2O3 films epitaxially grown by pulsed laser deposition

Numerous epitaxial LiNbO3 films, i.e,, LiNbO3(0001)/Al2O3(0001), LiNbO3(0001)/ Al2O3(11 (2) under bar0), and LiNbO3(11 (2) under bar0)/Al2O3(11 (2) under bar0) films, were grown by pulsed laser deposition Leu: deposition temperatures below 450 degreesC were used in order to reduce a Li deficient phase, LiNb3O8. Structural properties of the films, including twin formation, were investigated by X-ray theta -2 theta scan and pole figure techniques. Nonlinear optical properties of these films were investigated using the Marker fringe and the Senarmont methods. The nonlinear optical coefficients related to the SHG, i.e., d(31) and d(33), were measured and their values were found to be very close to the LiNbO3 single crystal values. It was also found that the SHG phi -scan can provide information on twin formations and in-plane orientation of the film. Electro-optic (EO) properties of the. films were also studied. Films with different orientations display large differences in their EO properties: the epitaxial LiNbO3(0001) films show little EO effects, but the LiNbO3(11 (2) under bar0) film shows a large quadratic EO behavior with an effective coefficient of 2.38x10(-15) m(2)/V-2.