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Stability of the beam quality of 0.98 mu m InGaAlAs tapered laser oscillators

Störungsempfindlichkeit der Strahlqualität von InGaAlAs Trapezlasern bei einer Wellenlänge von 0.98 Mikrometer


Optical Society of Korea:
CLEO/Pacific Rim '99. the Pacific Rim Conference on Lasers and Electro-Optics. Technical digest
Piscataway, NJ: IEEE, 1999
ISBN: 0-7803-5661-6
S.1097 ff
Conference on Lasers and Electro-Optics (CLEO)/Pacific Rim <3, 1999, Seoul>
Fraunhofer IAF ()
beam quality; feedback sensitivity; Halbleiterlaser; Rückwirkungsempfindlichkeit; semiconductor laser; Strahlqualität; tapered laser oscillator; Trapezlaser

We have investigated the beam quality and the astigmatism of tapered semiconductor laser oscillators under perturbation conditions to specify under which conditions such devices can be employed for direct applications such as material processing. 'In the recent years there has been a great interest in high-power high-brigthness laser diodes with a tapered gain structure. The superior beam quality of these devices opens a large variety of direct applications in material processing such as welding, cutting or surface treatment. The sensitivity to beam filamentation formation has been reduced by a low modal gain structure. Based on this structure highpower high-brightness tapered laser arrays with 25 W cw output power and near-diffraction limited beam quality of each single emitter have been fabricated. For the applications of single devices as well as arrays it is of great concern to specify the sensitivity of the beam quality to perturbations in general. Such perturbations can be optica l feedback from a metallic surface which can occur during material processing or current changes during the device lifetime which modify the internal source position. We report on the feedback sensitivity of the beam quality and the current dependence of the astigmatism which define the physical limits of the single devices in an array. The feedback in the experiment is created by a mirror in front of the large output aperture of the tapered laser after beam collimation. Variable attenuators provide different feedback levels.