EXCITON-POLARITONS IN SUPERLATTICES

The nonlocal semiclassical theory of the optical response of excitons in multiple quantum wells is formulated in a transfer-matrix scheme. The theory is applied to a derivation of the dispersion of exciton-polaritons in superlattices. In the long-wavelength limit the polariton dispersion is shown to reduce to that of a light wave in a uniaxial material, described by an effective (local) dielectric tensor: for TE polarization the polariton dispersion is that of the ordinary wave, while for TM polarization the dispersion is that of the extraordinary wave and describes longitudinal-transverse mixed modes. Numerical examples are given for polaritons in GaAs/AlAs superlattices.