How do we get to high laser intensities ?
In CPA, the ultrashort pulse is not amplified directly, but is first stretched and then amplified, before finally being recompressed. CPA reconciles two apparently conflicting needs: to have the highest fluence for efficient energy extraction, and to have minimum intensity to avoid the undesired nonlinear effects.
How do we characterize high intensities ?
Characterization of focal field formed by a large numerical aperture paraboloidal mirror and generation of ultra-high intensity (1022 W cm-2)