Highly efficient quasi-phase-matched second-harmonic generation by frequency doubling of a high-frequency superimposed laser diode

We report highly efficient blue-light generation by frequency doubling of a high-frequency superimposed laser diode, stabilized by a grating feedback technique, in a periodically domain-inverted LiTaO3 waveguide. To increase second-harmonic generation conversion efficiency, we enhanced the peak power of the laser diode by using a gain-switching method. Locking the oscillation wavelength of the laser diode by the grating feedback technique, we obtained 4.5 mW of average blue-light power with 13% conversion efficiency.