Dynamic many-body and nonequilibrium effects in a quantum dot microcavity laser

An interesting aspect of semiconductor quantum dot lasers is their potential for fast dynamical response. Since carrier relaxation is slowed down for discrete energy levels, it is generally agreed that nonequilibrium effects will have strong influence on dynamical behavior in quantum dot lasers. In this paper, we show that, furthermore, many-body effects should be taken into account. The reason is that the interplay of bandgap renormalization, population-hole burning and inhomogeneous broadening is crucial for understanding quantum dot laser dynamics. For example, when operating with a microcavity, the interplay gives rise to modifications of relaxation oscillation behavior that is beyond what can be described by the usual 2-variable rate equation treatment. The theory used in the simulations is based on a semiclassical approach, where the laser field and active medium are described by the Maxwell-semiconductor-Bloch equations. Many-body Coulomb effects are described in the screened Hartree-Fock approximation. Carrier-carrier and carrier-phonon collisions are treated within the effective relaxation rate approximation, with the effective rates estimated from a quantum mechanical approach. Current injection and carrier capture, details of the electronic structure, as well as influences of spectral-hole burning and state-filling in an inhomogeneously broadened quantum dot distribution are taken into account. This theory provides a microscopically consistent description of a quantum dot laser and allows one to perform parametric studies on time scales ranging from subpicosecond to nanoseconds. © 2010 SPIE.