High-efficiency LiNbO3 waveguide second-harmonic generation devices with ferroelectric-domain-inverted gratings fabricated by applying voltage

The characteristics of the ferroelectric-domain-inverted gratings fabricated by applying voltage at room temperature in Z-cut LiNbO₃ crystal were examined for waveguide quasiphase-matched second-harmonic generation (QPM-SHG) devices. Conditions suitable for reproducible fabrication of uniform grating structure were clarified. Devices with uniform and fan-out grating for green and blue light generation were fabricated, and the performances were examined. A normalized SHG efficiency as high as 150%/W was obtained in blue light generation device with uniform grating of 3 mm interaction length