High energy femtosecond fiber chirped pulse amplification system with adaptive phase control

We demonstrate increased peak power from an Yb fiber CPA system operating with strong self-phase modulation by shaping the spectral phase of the input pulses. An adaptive control loop used feedback from the output autocorrelation. We investigated pre-compensation of both SPM phase distortion at high energies, and residual dispersion from mismatched stretcher/compressor technologies at low energies. Phase shaping resulted in improved pulse quality with the autocorrelation peak typically increased by a factor of three compared to unshaped pulses. High-quality 800 fs, 65 µJ recompressed pulses were produced. This technique could benefit a wide variety of fiber amplifier systems and is self-optimising for operation at both low and high pulse energies