Improving the beam quality of single-grating spectrally combined fiber lasers with adaptive optics

Spectral combination is promising for diffraction-limited beam quality and single aperture beams. Unfortunately, beamlet deviations, linewidth broadening, and thermal aberrations inevitably degrade the beam quality. Many high-power laser systems integrate adaptive optics systems to maintain beam qualities. However, owing to the nature of incoherent combination, there is no well-defined wavefront in the spectrally combined beam, and whether phase compensations can enhance beam quality has not been discussed yet. We present the feasibility of improving the beam quality of spectral combined fiber lasers by adaptive optics. Simulations indicate that common path aberrations can be effectively corrected by adaptive optics, while beam quality degraded by displacement deviations and linewidth broadening cannot be improved. Additionally, the combined beam could be directly used as the beacon light in the propagation tunnel. To our knowledge, this study is the first to demonstrate that adaptive optics can improve the beam quality of spectrally combined fiber lasers and enable a further step toward diffraction-limited beam quality.