EXCITONIC POLARITONS IN SUPERLATTICES

The excitonic energies are computed in superlattices from the poles in the imaginary part of the susceptibility, using an appropriate Green' s function expression for the coherent amplitude function of the elect ron-hole pair. Solving the Maxwell equations, the polariton states are obtained and the optical properties are computed. The procedure inclu des the effects of coherence between the carriers and the electromagne tic field, and it does not require any type of additional boundary con ditions. Detailed calculations in GaAs/Ga1-xAlxAs superlattices show p olaritonic effects in the optical properties, in particular a peculiar fine-structure lineshape of the n = 1 and n = 2 hh and Ih excitons is obtained. A comparison with similar calculations in bulk GaAs clearly shows the roles of quantum confinement and of anisotropy in the super lattice.