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. When using a bulk grating stretcher, shaping increased the autocorrelation peak by a factor of 2.9, and with a fiber stretcher, shaping increased the autocorrelation peak by a factor of 3.4. 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.
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