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 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(2)< 3 is achieved for both, tapered laser oscillators and tapered amplifiers.