Excitonic polaritons in one-dimensional photonic crystals

Nonlocal investigations are presented for the exciton-photon coupling in one-dimensional periodic alternating layered structures consisting of two kinds of slabs (photonic crystals), in which excitons are present only in one of the two slabs. The lower branch of the excitonic polariton for this system is found to split into many small bands separated by small band gaps. This phenomenon is explained as the band splitting caused by the coherent interference of polaritonic waves in the periodic systems. The present nonlocal study also demonstrates a double exciton-photon coupling, in which the upper branch of the polariton couples again with the size-quantized exciton states.