Solitons in quadratic nonlinear photonic crystals - art. no. 047601

We study solitons in one-dimensional quadratic nonlinear photonic crystals with modulation of both the linear and nonlinear susceptibilities. We deriv e averaged equations that include induced cubic nonlinearities, which can b e defocusing, and we numerically find previously unknown soliton families. Because of these induced cubic terms, solitons still exist even when the ef fective quadratic nonlinearity vanishes and conventional theory predicts th at there can be no soliton. We demonstrate that both bright and dark forms of these solitons can propagate stably.