Microscopic study of relaxation oscillations in quantum-dot VCSELs

We propose a theoretical model to investigate the switch-on dynamics of electrically pumped quantum dot vertical-cavity surface-emitting lasers. The model is based on the self-consistently combined quantum dot-wetting layer Maxwell–Bloch equations incorporating microscopically calculated Coulomb and phonon-assisted scattering processes between the quantum dot and the quantum dot-embedding wetting layer states. Our approach allows the calculation of the time delay before lasing as well as of the frequency and damping rate of the appearing relaxation oscillation. We study their dependence on the strength of the injection current density and on the number of QD-layers and DBR-layers by using the finite-difference time-domain method. The results show that switch-on delay time is in inversely proportion to the injection current density while the frequency and the damping rate of relaxation oscillation are proportional to the current density. If we increase the numbers of QD-layers and DBR-layers the delay time becomes shorter, and the frequency and the damping rate become larger.

► We propose self-consistently combined quantum dot-wetting layer Maxwell–Bloch equations.
► Coulomb and phonon-assisted scattering processes are included.
► Switch-on dynamics of the quantum-dot vertical-cavity surface-emitting lasers is investigated
► Finite-difference time-domain (FDTD) method is used.
► Switch-on delay time and the frequency and the damping of relaxation oscillations are calculated.