Nonlinear Dynamics in Semiconductor Lasers - Abstract

Larkins, Eric

Simulation of the impact of nonequilibrium heating on semiconductor laser dynamics

We explore the role of the bipolar carrier plasmas on the performance of edge-emitting QW laser diodes using our simulation tools, Speclase and Dynlase. First, we show how CW optical modulation (gain/absorption bleaching) affects the carrier plasma distribution and beam quality. Next, we validate the electrical modulation response for a wide range of small- and large-signal operating conditions. Having validated our approach for quasi-equilibrium conditions, we turn our attention to non-equilibrium and nonlinear optical response. Using a microscopic model for the nonequilibrium carrier plasmas, we found that the subband carrier distributions can be described as Fermi-Dirac distributions with separate quasi-Fermi levels and temperatures and that optically-induced plasma dynamics are principally due to carrier density modulation (CDM) and carrier heating (CH). Surprisingly, both effects were found to be important up to very high frequencies (> 1 THz). The importance of CDM for the nonlinear optical response of the carrier plasma was demonstrated by directly including the plasma-induced gain and index dispersion in the simulation. Four-wave mixing (FWM) was observed in the simulations and validated with an rf spectrum analyser in nearly degenerate FWM experiments. Finally, we turn our attention to the long neglected role of hot optical phonons. At high current injection densities, the high energy relaxation rate of carriers captured by the QW can create a non-equilibrium or ?hot? LO phonon population. We include hot phonon effects in our simulations to explore their impact on the CW and direct modulation response of a high speed Fabry-Perot laser.