ASE contrast improvement in CPA ultra-intense laser chain

Summary form only given. Different possible solutions for improving the contrast consist in seeding the preamplifier with more energetic pulses, amplifying these energetic pulses via a low ASE preamplifier in the femtosecond regime and also temporally filtering the ASE versus the femtosecond pulse in a nonlinear interferometer before the power amplifiers. Preliminary results have been obtained by temporal filtering a millijoule level femtosecond pulse with a Sagnac interferometer in the nonlinear regime.