HIGHLY EFFICIENT GREEN-LIGHT GENERATION BY QUASI-PHASE-MATCHED FREQUENCY-DOUBLING OF PICOSECOND PULSES FROM AN AMPLIFIED MODE-LOCKED ND-YLFLASER

We report on first-order quasi-phase-matched frequency doubling of pic osecond pulses to the green, using a sample of periodically poled lith ium niobate. In cw mode-locked operation, 330 mW of average green powe r was generated with an average conversion efficiency of similar to 52 %. With a quasi-cw mode-locked pulse train an average conversion effic iency of similar to 65% was achieved, and 1.3 W of green power (averag e power within the 10-mu s pulse envelope) was produced. At these powe rs there was no significant photorefractive damage, as confirmed by me asured M(2) beam-quality factors of similar to 1.1 for both output fun damental and second-harmonic beams. (C) 1996 Optical Society of Americ a