Generation From Two-Dimensional (2) Nonlinear Photonic Crystals of Tetragonal Lattice Structure

Abstract—We investigate the effects of lattice spacing and domain-filling ratio on the wavelength dependence in second-har-monic generation (SHG) from two-dimensional (2) nonlinear photonic crystals (2-D NPC) on lithium niobate. Spectral coverage of 150 and 200 nm around 1.5 and 1.9 m in quasi-phase-matched (QPM) SHG is obtained by angular rotation of the NPC with a lat-tice periodicity of 20 20 and 29.5 29.5 m2, respectively. The SHG signals are shown to have off-axial propagation directions determined by the incident wavelength and the QPM vector. The intensity of the high-order reciprocal-lattice-vector (G mn)-as-sisted SHG signal is shown to depend on the domain-filling ratio. These observations are attributed to the unique dispersion of G mn together with the nonzero (2)(G mn) nonlinearity in the 2-D QPM-NPC having a tetragonal lattice structure. Index Terms—Nonlinear photonic crystals, quasi-phase-matching, second-harmonic generation (SHG). I