Barrier- and in-well pumped GaSb-based 2.3 µm VECSELs

We report on recent advances in the performance of GaSb-based optically-pumped vertical-external-cavity surface-emitting lasers (VECSELs) emitting at wavelengths around 2.3 µm. Both barrier and in-well pumped VECSELs have been fabricated and analysed. Both variants incorporate a diamond intra-cavity heat spreader as an efficient means for heat extraction from the active region. For barrier-pumping, a maximum output power of 1.5 W with a beam propagation factor of M2 <= 3 has been achieved at a heat sink temperature of -20°C. Using in-well pumping at 1.96 µm, the efficiency could be more than doubled, compared to barrier pumping, due to the significantly reduced quantum deficit, yielding a slope efficiency of 31% at a heat sink temperature of 10°C.