1.3 μm quantum dot lasers with single and stacked active layers

Long wavelength GaAs-based quantum dot lasers have been shown to have attractive characteristics including improved electronic confinement and low threshold at room temperature. However, nonradiative recombination and saturation of the ground state gain at low current density have limited performance. Stacking of multiple active layers has been successfully applied to QD lasers emitting in the 1.0 μm wavelength range to improve the ground state lasing performance, and recently used to obtain continuous wave (CW) operation in 1.3 μm QD lasers. More recently continuous wave operation has also been obtained with single 1.3 μm QD layers. In this talk we present the results on the low threshold CW room temperature operation of a single stack 1.3 μm QD laser and contrast its behavior with stacked QD lasers. We find that for stacked QD active regions, the layers must be separated by greater than 800 Å to fully recover the luminescence efficiency of a single QD layer. On the other hand, the single stack 1.3 μm QD laser exhibits a low CW threshold current of 4.1 mA, and a remarkably low CW threshold current density of 45 A/cm². At cryogenic temperatures broad-area devices operate with a threshold current density of 6 A/cm²