Long-wavelength lasers based on metamorphic quantum dots

We study a novel approach to extend a spectral range of GaAs-based structures up to 1.6 μm. The dependence of quantum dot (QD) light emission on the bandgap of surrounding matrix is employed by forming a QD array inside a metamorphic InGaAs epilayer. Specific growth regimes and the design of the metamorphic transient layers can provide a mirror-like morphology in combination with the effective dislocation trapping. It is shown that the wavelength of the QD emission can be controllably tuned in the 1.4-1.6 μm range by varying the composition of the metamorphic InGaAs matrix. Details of formation, fabrication and characterization of metamorphic-based diode lasers are presented. We demonstrate a lasing wavelength as long as 1488-1515 nm in the 20-80 °C temperature interval. The minimum threshold current density of that is 700 A/cm2 at room temperature. The external differential efficiency and the maximum pulsed power exceed 50% and 7 W, respectively. Issues of the metamorphic-based long-wavelength surface-emitting laser are also addressed.