Résumé:

Optical properties involving energy states that are not localized in the wells of superlattices are investigated. We show how the symmetry properties of these unconfined states can be easily understood by a perturbative calculation of a near-free-electron superlattice. The selection rules are found to be dependent on the layer thicknesses. The optical transitions of an (In,Ga)As-GaAs strained superlattice are calculated using a tight-binding model. We demonstrate that a transition previously considered forbidden is, in reality, symmetry allowed.