ANGULAR-DEPENDENCE OF PHASE-MATCHED 2ND-HARMONIC GENERATION IN A PHOTONIC CRYSTAL

Experimental measurements of the second-harmonic-generation intensity in centrosymmetric photonic crystals indicate that the efficiency of t his quadratic nonlinear process increases as the angle subtended by a reciprocal lattice vector and the second-harmonic field wave vector al so increases. This behavior is explained by the use of a simple theore tical model based on second-harmonic generation from a lattice of nonl inear bilayers that confirms the surface character of this nonlinear p rocess in this type of material. (C) 1998 Optical Society of America [ S0740-3224(98)02209-7].