Modeling of carrier dynamics in InGaAs/GaAs self-assembled quantum dot lasers

In this study, a theoretical model is used to simulate the lasing characteristics of InGaAs/GaAs self-assembled quantum dot lasers. The rate equation for InGaAs/GaAs is numerically solved using the fourth-order Runge-Kutta method. We consider the homogeneous and inhomogeneous broadening of the optical gain, both with and without considering the nonlinear gain. The results indicate that for a certain injected current, there is a specific homogeneous broadening (HB) with the best lasing performance when HB is near, comparable, or equal to inhomogeneous broadening for every laser-injected current. We show that if the linear optical gain is replaced by the total gain, the output power will reduce a little and the peaks will be more broadened and the maximum of the gain spectrum decreases. The time evolution of the photon number for different currents and different HBs is shown. The results indicate that by increasing the HB, the number of photons in the steady state and the delay in the starting oscillation will increase. In addition, we show that there is threshold coverage for quantum dots to begin lasing and an optimum quantum dot coverage in which the self-assembled quantum dot lasers operate with the lowest possible threshold current and maximum output power.