Quasi Phase Matching in Two-Dimensional Quadratic Nonlinear Photonic Crystals

We analyze quasi-phase-matched conversion efficiency of the five possible types of periodic two-dimensional nonlinear structures: Hexagonal, square, rectangular, centred rectangular and oblique. The frequency conversion efficiency, as a function of the two-dimensional quasi-phase-matching order, is determined for the general case. Furthermore, it is demonstrated for the case of a circular motif. This enables to determine the optimal motif radius for achieving the highest conversion efficiency. As an example for experimental techniques, we discuss the fabrication and nonlinear optical characterization of a rectangularly-poled stoichiometric LiTaO3 crystal.