Characterizing transient dynamics in vertical-cavity surface-emitting lasers

We implement an optical dynamical model for VCSELs. By including analytical expressions for the frequency-dependent susceptibility of the quantum well region. We investigate the transverse mode evolution during the turn-on and turn-off transients, accompanying the binary modulation. Our spatio-temporal description accounts for the lateral dependence of the slowly varying amplitude of the electric fields in both circular polarizations, that dynamically interact with carrier densities with opposite spin orientations. The model correctly includes the gain and, more important, the carrier-induced refractive index spectra that can strongly modify the transverse mode properties in the case of weak lateral guiding. In the opposite limit, we develop a simpler model which stems from the modal expansion of the spatio-temporal model. Fixed modal profiles and frequencies, determined from a given thermal lensing waveguide, are taken. We discuss the feasibility and accuracy of the modal expansion method by analyzing the transverse mode dynamics under turn-on and turn-off of the injection current.