HIGH-BRIGHTNESS TAPERED SEMICONDUCTOR-LASER OSCILLATORS AND AMPLIFIERS WITH LOW-MODAL GAIN EPILAYER-STRUCTURES

The dependence of the beam quality of tapered laser oscillators and am plifiers on the modal optical gain is demonstrated experimentally and theoretically for the first time. Tapered devices with high- (HMG) and low-modal gain (LMG) structures are compared in terms of output power and beam quality. At high-output powers the beam quality of LMG devic es is by a factor by ten better than the beam quality of high-modal ga in devices. The beam quality remains nearly unchanged up to power leve ls of more than 2-W continuous-wave (CW) where a beam quality factor o f M-2 < 3 is achieved for both, tapered laser oscillators and tapered amplifiers.