High-brightness 2.X µm semiconductor lasers

There is an increasing number of applications, which require compact and robust laser sources emitting in the 2-3 µm wavelength range. Based on semiconductor lasers, highly-efficient, small-footprint laser systems can be realized, having a long lifetime and the potential of reduced costs due to their mass-production capability. In recent years, semiconductor lasers based on the III-V compound semiconductor material system (AlGaIn)AsSb), emitting in the 1.8 µm to 3.0 µm wavelength regime (in the following abbreviated as 2.X µm) have reached a considerable level of maturity regarding spectral coverage, output power and device reliability. For the majority of the potential applications of these GaSb-based lasers, output power is not the only criterion, but the combination of high output power and good beam quality, i.e. high brightness, is the ultimate goal. This is more difficult to achieve for edge-emitting semiconductor lasers, than e.g. with classical solid state lasers. In this chapter we will give an overview of the recent advances concerning GaSb-based 2.X µm semiconductor lasers and describe the route to high brightness lasers, based on this material system.