Nonlinear photonic crystals with two-dimensional quasi-periodic and fractal superlattices

High quality z-cut LiNbO3 nonlinear photonic crystals with two-dimensional (2D) dodecagonal and fractal superlattices are successfully fabricated by applying the high voltage pulses. By collinear quasi-phase matching technique, second-harmonics at five wavelengths and ten wavelengths are observed simultaneously in one poled crystal, respectively. The same results can be obtained by rotating around the z axis by integrals of 30° in quasi-periodically poled crystal. In fractal nonlinear photonic crystal, the normalized conversion efficiency can be as high as 0.53%/mW for 499-nm second-harmonic laser spot. © 2012 Chinese Optics Letters.