Table of Contents:
In this thesis, optically pumped semiconductor disc lasers of two different designs, VECSEL(Vertical-External-Cavity Surface-Emitting-Laser) and VCSEL(Vertical-Cavity Surface-Emitting-Laser), are investigated in the framework of the Maxwell-Semiconductor-Bloch equations. This description accounts for the dynamical effects of the electronic system of the active material(here quantum wells) and allows to understand the resulting impact on the laser emission.
For quantum well pumping, it turns out, that dynamical scattering processes leads to nonequilibrium carrier distributions, which in consequence leads to a reduction of gain and an additional reduction of the pump absorption. In total, a sublinear power characteristic is observed. For barrier pumping, less nonequilibrium phenomena are observed as long as the in-well scattering is fast eqnough.
Due to the fact, that the largest part of the power loss in the laser is convertet into heat, the active mirror temperature raises resulting in a wavelength shift of the cavity resonance as well as the fundamental band edge of the actvie material. Although both shifts are toward lower energies, the different amplitudes of the shift result in net shift causing the so called thermal rollover.
In this thesis, this aspect of the power characteristic was analysed with a rate-equation approach, based on microscopical gain and loss calculations. The influence of the resonator and especially of the sub cavity formed by the active mirror was investigated leading to the statement, that the cavity design has to be set according to the demanded features of the device like e.g. low threshold or high maximal emission power.
In the last part of this thesis, the dynamic response of a coherent controlled optically pumped VCSEL was investigated. The results of an external experiment showing chirp dependent laser emission was explained by chirp-dependent bleaching of the pump absorption, where again nonequilibrium carrier distributions play a major role.