Optical lattices achieved by excitons in periodic quantum well structures

Photoluminescence and linear optical response from large-number multiple qu antum well structures, with a period in the vicinity of half the exciton re sonance wavelength, are dominated by the normal modes of the coupled wells. These show up in multiple linesplitting and a photonic band gap at Bragg r esonance. The photonic gap is identified by an enhanced Bragg reflection an d a corresponding weak absorption of the optical lattice. The strongly modi fied light-matter interaction for photons in the photonic gap is also manif est in the poor emission from the so-called super-radiant mode after excita tion in the free carrier continuum.