Spatio-temporal fluctuations and disorder in quantum dot lasers

The quantum dot laser is a complex nonlinear system in which light fields dynamically interact with the charge carriers in the dots and the embedding quantum well medium. In real laser systems, typical dot-to-dot variations in size, energy levels and material parameters exist. In addition, the dots are not equally positioned on a grid within the layers. The respective variance in quantum dot parameters and dot-to-dot distance depends on the material system and the epitaxial growth process of the particular quantum dot system. To elucidate the influence of spatial fluctuations, we calculate the temporal light field dynamics of quantum dot lasers with variable fluctuations in the characteristic dot parameters. The simulations on the coupled ultrafast spatio-temporal light-field and carrier dynamics in quantum dot lasers are based on a two-level Multi-Mode Maxwell-Bloch description. The constituent equations consist of coupled spatio-temporally resolved wave equations and Bloch equations for the carriers within each quantum dot of a dot ensemble constituting the active gain medium of a quantum dot laser. It is shown that the light field dynamics and the emission spectra are strongly determined by the nonlinear coupling between the light fields and the charge carrier plasma, spatially varying material properties of the quantum dot ensemble as well as device geometry and carrier injection.