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

Long-term stabilization of carrier-envelope phase (CEP) at the multi-mJ level imposes new constraints on the design of few-cycle laser systems based on chirped pulse amplification [1]. In particular, dispersion fluctuations must be avoided as much as possible. One option is to choose small pulse stretching factors and compress with compact components with limited amount of dispersion. The counter part of this choice is the resulting high B-integral induced by the high intensity level in the amplification stages and in the compression stage. Therefore the spectral phase of the amplified pulse becomes a function of the output pulse energy, which calls for an adaptive spectral phase compensator. In this presentation we demonstrate how an acousto-optic dispersive filter (AOPDF) [2] can be used not only to pre-compensate spectral narrowing but also to measure (DazScope software from Fastlite) the spectral phase induced by SPM and then compensate for the measured phase distortion.