Impact of dot size on dynamical characteristics of InAs/GaAs quantum dot lasers

TL;DR

This study investigates how the size of InAs/GaAs quantum dots affects the laser dynamics, revealing size-dependent variations in lasing characteristics, and providing insights for optimizing quantum dot laser performance.

Contribution

It introduces a detailed numerical analysis of quantum dot size effects on laser dynamics, including energy level calculations and rate equation simulations for InAs/GaAs QD lasers.

Findings

Larger QDs decrease photon number and modulation bandwidth.

Larger QDs increase turn-on delay, maximum power, and threshold current.

Smaller QDs are better for high-speed modulation applications.

Abstract

The purpose of this research is to study laser dynamics of InAs/GaAs Quantum Dot Lasers (QDLs) by changing QD energy levels. To date, most of the investigations have focused on only one of these circumstances, and hardly the result of change in the energy levels can be seen in lasing. In this work, in the first step, energy levels of lens-shape QDs are investigated by the eight-band k.p method, their variation for different QD sizes are surveyed, and recombination energies of the discrete levels are determined. Then, by representing a three-level InAs/GaAs QD laser, dynamics of such a laser device is numerically studied by rate equations in which homogeneous and inhomogeneous broadenings are taken into account. The lasing process for both Ground State (GS) and Excited States (ES) was found to be much sensitive to the QD size. It was observed that in larger QDs, photon number and bandwidth of the small signal modulation decrease but turn-on delay, maximum output power, and threshold current of gain increase. It was also found that for a good modulation, smaller QDs, and form the point of view of high-power applications, larger QDs seem better. Keywords: quantum dot lasers, QD size, energy level control, small signal modulation