Automated optimization of the temporal duration of a 21 fs, 4 mJ CPA laser system with high B-integral

An acousto-optic dispersive filter (AOPDF) is used to pre-compensate spectral narrowing and to measure (DazScope software from Fastlite) the spectral phase induced by SPM and then compensate for the measured phase distortion. The paper presents the results of SHG spectra versus chirp traces together with the extracted local chirp function for four states: initial state at low energy, coarsely optimized pulse at low energy, pulse at high energy with the same phase settings, finely optimized pulse at high energy. The change in energy dramatically changes the spectral phase of the amplified pulses. Simulations of the amplification in the laser chain with the software MIRO corroborate this result.