Spatial dispersion effects on the optical properties of a resonant Bragg reflector

In the recent literature, aspects of exciton-radiation interaction in multilayers have been discussed from the viewpoint of microscopic nonlocal optical response. This renewed interest has also revived a long lasting debate about the problem of additional boundary conditions in dispersive samples. In the present paper, the semiclassical framework for studying self-consistently the radiation-matter interaction in a dispersive multilayer medium is briefly reviewed, and applied to the case of a one-dimensional (1D) cluster of quantum wells under Bragg conditions. The optical response is computed as a function of quantum well number N from the super-radiant regime (for rather small N values) to the 1D Bragg reflector limit (→N∞). The different contributions of the radiation-matter interaction to the optical response are discussed by Feenberg's decomposition of the polaritonic matrix. The polariton dispersion curves of a quantum well superlattice are computed and compared with the photonic dispersion curves due to the background dielectric function modulation. Finally, the modification of the photonic bands close to a resonance of the material system is discussed using selected numerical examples.