Nonlinearity- and Dispersion-Controlled High-Energy All-Fiber Femtosecond Laser System with Peak Power Exceeding 0.5 GW.

A monolithic all-fiber high-energy chirped pulse amplification (CPA) system with a managed large dispersion is demonstrated. Considering the nonlinearity in the amplification system, two temperature-tuning cascaded chirped fiber Bragg gratings (CFBGs) with a large dispersion of 200 ps/nm are employed as stretchers to stretch the pulse duration to more than 2 ns in the time domain. The main amplifier, with centimeter-level length, a large mode area, and high-gain silicate glass fiber, increases the energy to 293 μJ at 100 kHz. A reflective grating pair with a high density of 1740 lines/mm is used to compress the large-dispersion chirped pulse into a compact structure. Owing to the high-order dispersion pre-compensation by the CFBGs and the large-sized grating with high diffraction efficiency, we achieved a compressed pulse duration of 466 fs with a maximum pulse energy of 250 μJ, corresponding to a compression efficiency of more than 85% and a well-preserved beam quality of M2 < 1.3. To the best of our knowledge, this is the highest pulse energy ever reported in a monolithic fiber femtosecond amplifier.