Ultrafast carrier dynamics in tunnel-injection quantum-dot lasers

Increased modulation speed in quantum-dot lasers is possible by means of a tunnel-injection design. The concept was introduced to improve the dynamical properties of semiconductor lasers by avoiding the problem of hot carrier injection, which increases the gain nonlinearity thereby limiting the modulation capabilities. Cold carriers are efficiently provided via an injector quantum well that is tunnel coupled to excited QD states. We study the ultrafast carrier population dynamics in tunnel-injection lasers by comparing LO-phonon-assisted tunneling processes and Coulomb-scattering-assisted processes.