Gap solitons in nonlinear spatiotemporal photonic crystals and gratings

We have generalized the concept of nonlinear periodic structures to dielectric systems that show arbitrary spatial and temporal variations of the refractive index. Nonlinear pulse propagation through these spatiotemporal photonic crystals can be described, for shallow nonstationary gratings, by coupled mode equations which are a generalization of the traditional equations used for stationary Bragg gratings. Novel gap soliton solutions are found analytically. They represent a generalization of the gap solitons in static photonic crystals and resonance solitons found in dynamic gratings.