Gain and propagation in quantum well amplifiers

Abstract

We investigate systems of one, two, and multiple quantum wells separated by thick barriers in such a way that the electronic states are localized in each well. However, the different quantum wells are coupled due to the electromagnetic field. It is shown that the loss of translational invariance in the growth direction affects the interaction between the optical field and the interband polarization. Multiple reflections of the optical field between the different quantum wells occur and significantly modify the interaction dynamics between the optical field and each well. Depending on the geometry and initial conditions the propagation and amplification dynamics of a short pulse in such a system are investigated. An energy transfer between different quantum wells mediated by the laser pulse is observed. Time resolved reflected and transmitted signals for different geometries and numbers of quantum wells are calculated. The influence of Coulomb effects on the reflected and transmitted pulses is studied. It is shown that the interaction dynamics between the laser pulse and the sample shows a strong dependence on the number of quantum wells and the separation between the different wells.