Enhanced modal gain of multilayer InAs/InGaAs/GaAs quantum dot lasers emitting at 1300 nm

The optical properties of multilayer InAsInGaAs quantum dots (QDs) with different GaAs barrier thicknesses have been investigated. The photoluminescence (PL) intensity is found to increase with increasing GaAs barrier thickness. For thicknesses larger than 40 nm the PL intensity increases linearly with the number of the QD layers, with a considerable narrowing of the full width at half maximum (from 33 to 26 meV for active regions consisting of three QD layers). This growth protocol has been applied to laser structures containing stacked InAsInGaAs QD layers. The broad area processed devices exhibit a modal gain as high as 30 and 41 cm-1 for structures embedding five and seven QD layers, respectively, which corresponds to 6 cm-1 per QD layer. The internal quantum efficiency and the transparency current density per QD layer were approximately 70% and 10 A cm2, respectively, for both structures.