Vertical external cavity surface emitting PbTe/CdTe quantum dot lasers for the mid-infrared spectral region

Optically pumped vertical external cavity surface emitting lasers (VECSELS) emitting in the mid-infrared range are demonstrated with an active structure based on PbTe quantum dots (QDs) embedded in CdTe. In contrast to Stranski-Krastanov QDs, the PbTe QDs are fabricated by a strain-free synthesis method consisting of a molecular beam epitaxy growth step followed by a post-growth-annealing step. The laser emission of the VECSELs covers a wavelength range between 3.5 and 4.3 μm by changing the temperature from 85 to 240 K. The threshold power is lower than 100  mW(P) and the output power is more than 50  mW(P) at low temperature.