Efficient continuous wave second harmonic generation pumped at 1.55 µm in quasi-phase-matched AlGaAs waveguides

We have fabricated quasi-phase-matched AlGaAs waveguides for continuous-wave second-harmonic generation (SHG) pumped around 1.55 microm. We find that the losses, which limit the conversion efficiency of this type of waveguide, are resulted from two corrugations--the initial template corrugation and the regrowth-induced domain-boundary corrugations. We are able to reduce the waveguide loss by improving the growth conditions. The waveguide loss is 6-7 dB/cm at 1.55 microm, measured using the Fabry-Perot method. A record internal SHG conversion efficiency of 23 %W-1 for AlGaAs waveguides is achieved using a 5-mm-long waveguide with a pump wavelength of 1.568 microm.