Second-harmonic generation in two-dimensional periodically poled lithium niobate using second-order quasiphase matching

Two-dimensional nonlinear photonic crystals of lithium niobate with square lattices were fabricated. In these crystals, efficient quasiphase-matched second-harmonic generation was demonstrated by using second-order quasiphase matching. As a mode-locked Nd:yttritium-aluminum-garnet laser at 1064 nm with 35 ps pulse was used, we obtained an average power of 0.86 mW at 532 nm with 2.73 mW input, which corresponds to 42% internal conversion efficiency. The variations of second-harmonic output with crystal temperature and incident angle were measured. In addition, the relation between the second-harmonic output and reversed duty cycle was studied. All the experimental results are well consistent with simulations. (C) 2003 American Institute of Physics.