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High-power diode lasers in the mid-infrared wavelength range between 1.8µ;m and 2.3µm have emerged new possibilities for applications like processing and accelerated drying of materials, medical surgery, infrared countermeasures or for pumping of solid-state and semiconductor disc lasers. We will present results on MBE grown (AlGaIn)(AsSb) quantum-well diode laser single emitters with emitter widths between 90µm and 200µm. In addition laser bars with 20% or 30% fill factor have been processed. More than 30% maximum wall-plug efficiency in cw operation for single emitters and laser bars has been reached. Even at 2200nm more than 15W have been demonstrated with a 30% fill factor bar. Due to an increasing interest in pulsed operation modes for these mid-infrared lasers, we have investigated single emitters and laser bars at 1940nm for different pulse times and duty cycles. More than 9W have been measured at 30A with 500ns pulse time and 1% duty cycle without COMD for a single emitter. Most applications mentioned before need fiber coupled output power, therefore fiber coupled modules based on single emitters or laser bars have been developed. Single-emitter based modules show 600mW out of a 200µm core fiber with NA=0.22 at different wavelengths between 1870nm and 1940nm. At 2200nm an output power of 450mW ex fiber impressively demonstrates the potential of GaSb based diode lasers well beyond wavelengths of 2µm. Combining several laser bars, 20W out of a 600µm core fiber have been established at 1870nm. Finally for a 7 bar stack at 1870nm we have demonstrated more than 85W at 50A in qcw mode

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Especially for fiber pump applications there is a strong demand for high-brightness diode lasers in the 10W power regime. Broad-area and tapered laser concepts seem to be the most promising candidates for high brightness, which is proportional to output power divided by beam quality. Within this talk we give a comparison of both concepts identifying the possibilities and limitations of both concepts.Whereas fast axis far fields show mostly a current independent behaviour, for broad-area lasers near-and farfields in the slow axis suffer from a strong current and temperature dependence, limiting the brightness. For tapered diode lasers the brightness is limited by the temperature characteristics of M 2 and astigmatism. Therefore for both concepts it is essential to have lasers with excellent thermal management, which can be realized by 4-5mm long resonators in combination with wall-plug efficiencies well beyond 60%.To fulfill these issues, we have realized MBE grown InGaAs/AlGaAs broad-area and tapered lasers with resonator lengths between 4mm and 5mm and 45° fast axis far field emitting at 976nm. For a 5mm long broadarea laser with 90µm stripe width a beam parameter product of less than 5.9 mm x mrad (M 2 <10) has been achieved at 10W with a slope efficiency of 1.1W/A and a maximum wall-plug efficiency of 65%. For a tapered laser with a taper angle of 4° and 5mm resonator length, 10W have been demonstrated with a slope efficiency of 1.05W/A and a maximum wall-plug efficiency of 56%. Beam quality is below 3 up to 8W.