Microcavity polaritonlike dispersion doublet in resonant Bragg gratings

Periodic structures resonantly coupled to excitonic media allow the existence of extra intragap modes (Braggoritons) due to the coupling between Bragg photon modes and bulk excitons. This induces unique dispersive features, which can be tailored by properly designing the photonic band gap around the exciton resonance. We report that Braggoritons realized with semiconductor gratings have the ability to mimic the dispersion of quantum-well microcavity polaritons. This gives rise to peculiar nonlinear phenomena, such as slow-light-enhanced nonlinear propagation and an efficient parametric scattering at two magic frequencies.