Theoretical characteristics of quantum dot laser through modeling

Gain characteristics of injection lasers based on self-organized quantum dots (QD) were studied for two systems: InGaAs QDs in AlGaAs matrix on GaAs substrate and InAs QDs in an InGaAs matrix on an InP substrate. A ground to excited state transition was observed with increasing threshold gain. The current density of the model gain was calculated for the QD-on-GaAs and the QD-on-InP injection lasers. Two characteristic regions are observed in the dependences of the gain and the lasing wavelength on current density in both systems of QDs. These regions are attributed to the ground and excited state lasing in a QD array, respectively. Raising the current leads first to saturation of the QD ground state gain and then to a transition to lasing via excited states of QDs. The latter is characterized by three times higher gain saturation level. The higher the QD density, the higher both the transparency current density and also the gain saturation level.