Type I quasi-phase-matched blue second harmonic generation with different polarizations in periodically poled LiNbO3

First-order type I quasi-phase-matched (QPM) EYω+EYω→EZ2ω blue second-harmonic generation was demonstrated in periodically poled LiNbO3 with period of 14.5 μm using d31. 52 μJ of harmonic blue light at 0.473 μm was generated pumped by 114 μJ 35 ps pulse laser at 0.946 μm at 150 °C with a conversion efficiency of 45.6%. The average conversion efficiencies of 41.3% and 19% were also obtained at 150 °C, respectively, in the conventional first- and third-order QPM EZω+EZω→EZ2ω blue second-harmonic generation at 0.473 μm. The temperature acceptance bandwidths of 20 mm length periodically poled LiNbO3 with first-order grating periods of 14.5 and 4.5 μm are 2.0 and 0.9 °C, respectively. The larger acceptance bandwidths and grating period for EYω+EYω→EZ2ω than those for EZω+EZω→EZ2ω enhance the frequency conversion efficiency, which shows the polarization dependence of quasi-phase matching.