In this work, the ultrafast gain dynamics of a quantum dot (QD)-based semiconductor optical amplifier (SOA) is modeled on the basis of semiconductor Bloch equations that include microscopically calculated nonlinear scattering rates between QD carriers and the surrounding carrier reservoir. This enables us to separately study the dynamics of electrons and holes inside the device as well as the coherent effects related to the fast polarization dynamics. We show that the optical pulse power and the dephasing time of the polarization mainly affect the gain depletion inside the active region, while the electric injection current density and thus the internal carrier dynamics influence the gain recovery. We observe that carrier-carrier scattering is the source of desynchronized behavior of electrons and holes in the recovery dynamics of QD-based SOAs. The amplification of pulse trains in the SOA predicted by our model agrees well with experimental data.

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Abstract-We investigate the nonlinear dynamics of a quantum-dot laser coupled to an electro-optic modulator using the Lang-Kobayashi model. We determine the effect of the detuning between the EOM and the QD laser and the influence of the static phase shift on the QD laser dynamics. The electrooptical modulator's model is based on semiconductor MaxwellBloch equations with voltage dependent loss rates.