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

Abstract

Numerous epitaxial LiNbO3 films, i.e., LiNbO3(0001)/Al2O3(0001), LiNbO3(0001)/Al2O3(1120), and LiNbO3(1120)/Al2O3(1120) films, were grown by pulsed laser deposition. Low deposition temperatures below 450°C were used in order to reduce a Li deficient phase, LiNb3O8. Structural properties of the films, including twin formation, were investigated by X-ray θ-2θ 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 φ-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(1120) film shows a large quadratic EO behavior with an effective coefficient of 2.38×10×15 m2/V2.