Impact of Dot Size on Dynamical Characteristics of InAs/GaAs Quantum Dot Lasers

The purpose of this research is to study numerically laser dynamics of InAs/GaAs Quantum Dot Lasers (QDLs) with different QD sizes. To date, most of investigations have focused just on change of QD energy levels by size or laser dynamics of QDs of constant/fixed energy levels. 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, the results are used in a four-level InAs/GaAs QD laser, dynamics of such a laser device is studied numerically by rate equations in which homogeneous and inhomogeneous broadenings of the optical gain are taken into account. In this work we study QDs of diameter 15, 20 and 25 nm which are shown to have at least three electronic discrete energy levels in the QD. Lasing from both Ground State (GS) and Excited States (ES) was found to be much sensitive to the QD size. Increase in turn-on delay, maximum output power, and threshold current of lasing and decrease in photon number and bandwidth of the small signal modulation by increasing the QD size have been observed. It was also found that for an optimized modulation, smaller QDs, and from the point of view of high-power applications, larger QDs seem better.