In this talk the current status of group III-Antimonide based semiconductor lasers, emitting in the 2 µm to 2.5 µm infrared spectral range, will be reviewed. Such lasers are needed for materials processing and laser surgery as well as for spectroscopic sensing and medical diagnostics. To cover this wavelength range GaInAsSb/AlGaAsSb quantum well (QW) lasers grown on GaSb substrates are best suited. The growth of the epitaxial layer sequence is almost exclusively performed by solid-source molecular-beam epitaxy (MBE). Valved cracker effusion cells are employed as As and Sb sources for the reproducible growth of lattice-matched or deliberately strained GaInAsSb and AlGaAsSb quaternary layers of different compositions.

For broad area lasers emitting at 2 µm, high power efficiencies (~25%) and output powers of 2 W in cw mode (>9 W in pulsed mode) have been achieved at room-temperature. Laser bars with 19 emitters show at the same wavelength and temperature a cw output power as high as 21 W. To serve applications which require a better slow-axis beam quality than that provided by broad area lasers, the tapered laser concept has been adopted. Such lasers yield at 1.9 µm a nearly diffraction limited output with a beam quality factor of M²<1.7 up to an output power of 1.5 W, resulting in a brightness of 30 MW/cm².

Optically pumped Vertical-External-Cavity Surface-Emitting Lasers (VECSELs) are attracting considerable current interest as an alternative to edge-emitting semiconductor diode lasers. VECSELs combine a high quality circular output beam, which is a feature of classical solid state lasers, with the wavelength versatility of a gain medium composed of semiconductor quantum structures. Group III-Antimonide based VECSELs composed of a GaInAsSb/AlGaAsSb QW active region and a GaSb/AlAsSb distributed Bragg reflector (DBR) emitting at 2.3 µm have been demonstrated. With just thermoelectric cooling to -20°C a maximum cw output power of 1.5 W with M²<3 has been achieved, with the VECSEL chip bonded to an intra-cavity diamond heat-spreader for efficient heat removal.

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