A novel active region concept for highly efficient GaSb-based optically in-well pumped semiconductor disk lasers
A novel active region concept for GaSb-based optically pumped mid-infrared vertical external cavity surface emitting lasers (VECSELs, also referred to as optically pumped semiconductor disk lasers - OPSDLs) is presented. The concept is based on GaxIn(1-x)As(y)Sb(1-y) type-I quantum wells (QWs) embedded between AlAs(0.08)Sb(0.92) barrier layers designed for optical in-well pumping where the pump absorption at pump wavelengths between 1 µm and 2 µm takes place exclusively in the active QWs. This concept provides several advantages such as a high modal gain, the suppression of thermal leakage currents, and an improved thermal conductivity of the active region compared to a conventional GaInAsSb/AlGaAsSb active region design. Using the novel design approach an in-well pumped VECSEL emitting at 2.24 µm has been realized, yielding at a heat sink temperature of 20°C in continuous-wave operation a power slope efficiency of more than 32% and an absorption of the 1.96 µm pump light of more than 50% without pump recycling, These data constitute a significant improvement in device performance compared to previously reported data on in-well pumped GaSb-based VECSELs.