Application of self-organized quantum dots to edge emitting and vertical cavity lasers

Abstract

Self-organised quantum dots (QDs) are used successfully as active media of edge emitting and vertical cavity lasers. Threshold current densities at room temperature (RT) of 60 A/cm 2 for edge emitting lasers are measured in four side cleaved geometry. High internal (>96%) and differential (70%) efficiencies are obtained for InGaAs–AlGaAs lasers based on vertically coupled QDs. 1.5 W continuous wave operation at RT is demonstrated. Vertical cavity surface emitting lasers (VCSELs) based on QDs demonstrate threshold current densities down to 170 A/cm 2, comparable to the best values obtained for quantum well (QW) VCSELs, and total threshold currents as low as 67 μA. QD VCSELs demonstrate a reduction in the total current vs. aperture size down to 1 μm apertures due to reduced nonequilibrium carrier spreading out of the injection area as compared to QW VCSELs. QD lasers exhibit a much larger gain, differential gain and smaller line width enhancement factor as compared to conventional QW devices. These are clear inidcations that QD lasers will significantly overcome the performance of QW lasers in the future.