Reduced pump-requirement for group-velocity slowdown in quantum-dot quantum-coherence

In this paper, the many-body aspects and the differences to the independent-particle treatment of quantum coherence in QDs are discussed. For investigation the semiconductor Bloch equations, modified for a Lambda system, is used. A relatively detailed description of the electronic states of a coupled QD-QW system and the coupling of these states via collisions in the relaxation rate approximation is included. A structure consisting of InAs pyramidal dots with a base of 12 x 12 nm and height 6 nm on a wetting layer of thickness 1 nm embedded in a GaAs QW is chosen for the study. Here, the slow-down factor S, which is a measure of the refractive index changes resulting in optical group-velocity reduction and thus of interest for applications such as optical storage, is focused.