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The dependence of the beam quality of tapered laser oscillators and amplifiers 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 devices is by a factor of ten better than the beam quality of high-modal gain devices. The beam quality remains nearly unchanged up to power levels of more than 2-W continuous-wave (CW) where a beam quality factor of M/sup 2/<3 is achieved for both, tapered laser oscillators and tapered amplifiers.