Tuning effects in optimisation of GaAs-based InGaAs/GaAs quantum-dot VCSELs

The comprehensive optical-electrical-thermal-recombination self-consistent simulation of an operation of quantum-dot (QD) VCSELs is used to optimise their structure for GaAs-based oxide-confined QD VCSELs predestinated for the second-generation 1.3 mu m optical-fibre communication. It has been found that, contrary to a general belief of lasing thresholds of QD lasers inversely proportional to their density, for any design of QD VCSELs, there exists an optimal QD density ensuring its lowest lasing threshold. Besides, in intentionally strongly detuned QD VCSELs, to reach the desired 1.30-mu m radiation, it is superfluous to improve uniformity of their QDs because their lasing thresholds are surprisingly distinctly lower for less uniform QDs. Then for these devices more optimal are somewhat non-uniform QDs and a necessary optical gain may be achieved with the aid of an increasing QD density. (c) 2008 Elsevier B.V. All rights reserved.