Abstract

Quantum Dots (QDs) have been the subject of much attention due to their highly discrete band structure which allows for the emission of highly monochromatic light. Lasers can be made to produce pulses using a technique called mode-locking (ML), but QDs lasers which have not intentionally been mode-locked have still been observed exhibiting the same pulsing behaviour. The purpose of this research is to create a simulation of the dynamics of a QD laser to attempt to better understand the mechanism behind the observed mode-locking effect.

To study this, a simulation of a QD laser system was created in COMSOL Multiphysics 5.4 based on a theoretical model which uses a quantum perturbation theory to provide a detailed treatment of carrier-light interactions to model the impact that four wave-mixing (FWM) has on the electric field. This simulation was used to recreate results from simulations based on a time domain travelling wave (TDTW) model as well as experimental data to assess how well the perturbation theory model is able to match the data.

It was found that the simulation was able to produce results indicating the presence of lasing, but due to only simulating a single dot it is unable to properly show inhomogeneous gain broadening and mode-locking. Though this model shows potential for a variety of applications, it will need to be further enhanced to include multiple QDs and cavity modes to act as a more accurate and effective tool.