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

First-order type I quasi-phase-matched (QPM) 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 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 than those for enhance the frequency conversion efficiency, which shows the polarization dependence of quasi-phase matching.