Frequency-doubling of a CW fiber laser using PPKTP, PPMgSLT, and PPMgLN

Second-harmonic generation (SHG) in PPKTP, PPMgSLT, and PPMgLN crystals is analyzed by frequency-doubling CW light from a 1064 nm fiber laser over a range of powers up to 10 W. Data for fundamental powers less than 3 W is used to determine the effects of the fundamental laser linewidth on SHG and to identify imperfections in the periodicity and boundary sharpness of the crystals' poled domains which can reduce SHG. Data for fundamental powers greater than 3 W is used to diagnose and model limiting effects on SHG such as pump depletion and thermal dephasing. Thermal dephasing was found to reduce second-harmonic power by 25% or more for input fundamental powers approaching 10 W.