Exciton-photon interaction in low-dimensional semiconductor microcavities

The structure of the photon states and dispersion of cavity polaritons in s emiconductor microcavities with two-dimensional optical confinement (photon wires), fabricated from planar Bra,og structures with a quantum well in th e active layer, are investigated by measuring the angular dependence of the photoluminescence spectra. The size quantization of light due to the wavel ength-commensurate lateral dimension of the cavity causes additional photon modes to appear. The dispersion of polaritons in photon wires is found to agree qualitatively with the prediction for wires having an ideal quantum w ell, for which the spectrum is formed by pairwise interaction between excit on and photon modes of like spatial symmetry, The weak influence of the exc iton symmetry-breaking random potential in the quantum well indicates a mec hanism of polariton production through light-induced collective exciton sta tes. This phenomenon is possible because the light wavelength is large in c omparison with the exciton radius and the dephasing time of the collective exciton state is long. (C) 1998 American Institute of Physics. [S1063-7761( 98)01210-4].