Improving the Beam Quality in a High-Power Femtosecond All-Fiber System

In this letter, we present beam quality improvement in a 50-W-class nonlinear chirped pulse amplification (NCPA) femtosecond all-fiber system. By exploring the group delay dispersion management, we manipulate the nonlinear spectrum broadening, which can not only alleviate the spatial deterioration caused by fundamental mode saturation, but also enable significant pulse compression under the influence of the soliton effect. This work offers insight into the design of the NCPA all-fiber laser system, providing guidelines on simultaneously realizing good beam quality and ultrashort pulses.