Hybrid mode phase matching and effective nonlinear coefficient for second harmonic generation in biaxial waveguides

Phase matching between fundamental and second harmonic hybrid guided modes in nonlinear biaxial planar waveguides is determined for the first time based on principal axes orientations of the film, substrate, and cover. We have derived an expression for the effective nonlinear coefficient D/sub eff/ of hybrid modes in a biaxial waveguide and have calculated this coefficient numerically along the effective index phase match loci for these modes supported by a POM waveguide surrounded by isotropic media. The optimum phase matching orientations are determined for a fixed waveguide thickness. Dispersion of the principal indexes is considered.