The semiconductor heterostructure design and lasing characteristics of an optically in-well pumped (AlGaIn)(AsSb)-based vertical-external-cavity surface-emitting laser (VECSEL) emitting at 2.35μm are presented. The pump absorption in the active quantum wells at 1.96μm has been enhanced by a higher-order microcavity resonance. VECSEL operation in-well pumped by a thulium-doped fiber laser has been demonstrated. Compared to a VECSEL barrier pumped at 1μm, the in-well pumped device reaches a significantly higher power efficiency, and thus a higher output power at a given pump power, due to the smaller quantum deficit and hence reduced internal heat generation. Using an intracavity SiC heat spreader, a cw output power in excess of 3W has been achieved at a heat sink temperature of −15°C, and still more than 2W at +15°C.

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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

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