Beam pattern and filling factor improvement for a Cassegrain three-pass amplifier using a new shape of optimized serrated apertures

The upgrade of the actual large laser facilities (GEKKO XII in our case) implies an increase of filling factor avoiding generation of high spatial-frequencies. To reach that purpose we intend to construct the beam using serrated aperture with optimized shape. The performances of our system lead after simulation to 70% filling factor with less than 2% fluctuation on laser pattern intensity map. As only a very few articles were written on that subject although it is not very new, this paper includes a theoretical approach of the serration effects. It presents mainly results from simulation and some experimental data.