High-quality energy-scalable femtosecond pulses from a fibre-based chirped pulse amplification system via adaptive pulse shaping

Diode-pumped ytterbium-doped fibre lasers, coupled with the chirped-pulse amplification (CPA) technique, are promising for realising compact ultrafast laser systems with variable repetition rates. However, energy scaling in such a system is nontrivial, as the accumulation of high-order material dispersion and nonlinear phase modulation degrade the pulse quality upon compression. In our previous work, we demonstrated the generation of high-fidelity femtosecond pulses with a repetition rate of 50MHz in a fibre CPA system through the use of an adaptive pulse pre-shaping technique that compensated for high-order dispersion in fibres with a total length of <12m and a B-integral of up to 1.6 π rad. In this paper, we show the versatility of adaptive pulse pre-shaping to generate a high-quality pulse train with a variable repetition rate and energy in a fibre CPA system consisting of a 1km fibre stretcher with a B-integral reaching 2.2 π rad