Growth of epitaxial LiNbO3 films on sapphire substrates and their nonlinear optical properties

Abstract

Epitaxial LiNbO3 films, i.e., LiNbO3(0001)/Al2O3(0001), LiNbO3(0001)/Al2O3(11 (2) under bar 0), and LiNbO3(11 (2) under bar 0)/Al2O3(11 (2) under bar 0) films, were grown by the pulsed laser deposition. By varying the growth conditions, it was possible to control various growth behaviors, i.e., twin-ratios and crystal orientations. The nonlinear optical properties of the films including the second harmonic generation (SHG) and electro-optic (EO) properties were investigated. The SHG patterns of LiNbO3(0001)/Al2O3 (0001) films were strongly dependent on their twin-ratios. In order to analyze them, the contributions of the structural twins and polarization domains were taken into account. The linear EO property of the LiNbO3(0001)/Al2O3(0001) film was found to be as good as that of single cystal. However, the LiNbO3(11 (2) under bar 0)/Al2O3(11 (2) under bar 0) film shows a very large quadratic EO behavior with an effective coefficient of 2.38x10(-15) m(2)/V-2.