4.7 W continuous-wave (CW) and 11.7 W quasi-CW output power have been demonstrated for laser diodes based on six-fold stacks of InGaAs/GaAs quantum dots. Lifetimes beyond 3000 h at 1.0 and 1.5 W output power and 50degreesC heatsink temperature were measured. The output power is limited by catastrophic optical mirror damage occurring at 19.5 MW/cm(2) on the front facet

The facet heating of a single-quantum well InGaAs/AlGaAs broad-area high-power laser-diodes emitting at 940 nm was reduced by the introduction of a 30 µm long current blocking region located at the front facet of the laser, also increasing the level of catastrophical optical mirror damage. The blocking of the pump current close to the facet reduces the carrier density and then the surface recombination current. The temperature rise of 2 mm long and 200 µm wide lasers is reduced by a factor of 3-4

The longitudinal carrier density distribution of an InGaAlAs high-power broad-area semiconductor laser has been measured using spontaneous emission from the side of the device. The laser shows continuously increasing carrier densities on the facet with the high reflectivity coating (reverse facet). This has a major impact on the efficiency and the lifetime of the laser. This behavior is in good agreement with one-dimensional calculations for the longitudinal carrier distribution

We use a near-field microscopic technique to probe photoluminescence from the edge area of a quantum well. Near the edge, surface recombination gives rise to a gradual variation of the photoluminescence signal on a micrometer length scale. The overall shape in this transition region depends strongly on the excitation intensity. From solving two dimensional diffusion equations, we deduce the surface recombination velocity and the diffusion length. It is shown that the surface recombination velocity decreases with increasing intensity due to the saturation of nonradiative defect states

Semiconductor lasers with high beam quality and high optical output power are very attractive for a variety of applications such as optical pumping of solid-state lasers, fiber amplifiers and medical treatment. When easy and lowcost fabrication is a further requirement, devices based on tapered gain sections are the most promising candidates . Low modal gain, single quantum well InGaAs/AlGaAs devices emitting at 1040 nm were grown by molecular beam epitaxy. The lateral design consists of a tapered gain guided and a ridge-waveguide section having an overall length of 2.5mm. An output power of more than 1 1 W in qcw mode, lifetimes of more than 20,000 h and a record value for the beam quality factor M2 of less than 1 .5 up to a cw output power of 3 .5 W are achieved resulting in an improved brightness of more than 255 MW/(cm2sr). In addition an external-cavity diode laser including a ridge-waveguide tapered amplifier structure is demonstrated to emit more than 2 W cw. The wavelength is tunable over a 60 nm range centered at 1 020 nm. The beam quality parameter M2 remains below 1 .4 for output powers of 1 W over the whole range demonstrating the nearly diffraction limited behaviour.