The influence of the conduction-band nonparabolicity and Coulomb coupling between different electronic subbands and different hole subbands on gain, absorption, and refractive index in semiconductor heterostructures is investigated. We implement these features into a fully microscopic approach. At low carrier densities, the nonparabolicity leads to a steeper increase of the absorption for increasing transition energy. In this regime, the Coulomb subband coupling allows for a shift of oscillator strength to energetically lower transitions. In the gain regime, the conduction-band nonparabolicity is shown to reduce the gain width for a given carrier density and to strongly modify the corresponding refractive index. The Coulomb coupling is especially important to determine the correct energetic position and density dependence of the gain maximum. In addition, it leads to a steeper transition from the gain to the absorptive region.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Electrical and Electronic Engineering