Efficient second-harmonic generation in three-dimensional LiNbO3 optical waveguide

Highly efficient second-harmonic generation using a titanium in-diffused LiNbO3 three-dimensional optical waveguide was performed with the cw Nd : YAG laser at 1.064-μm wavelength. The phase-matching condition to convert the TE00 fundamental frequency to the TM00 or TM20 second harmonic was demonstrated by adjusting the crystal temperature. The conversion efficiency is 1.5×10−4 at 2-mW fundamental input power under the phase-matching condition. By using a low-loss LiNbO3 optical waveguide, equipped with highly reflective cavity mirrors on the input and output surfaces, parametric oscillation is expected.