High contrast ratio Nd:glass front-end laser system with a femtosecond seed source

We report a front-end system that provides selection, stretching and amplification of 240 fs pulses from sub-nJ level up to 5 mJ with contrast ratio >10 7 . Laser system consists of a master oscillator GLX-200, single pulse selector, diffraction-grating stretcher, regenerative amplifier and electrooptical deflector. It is shown that spectral shaping reduces spectrum narrowing in amplifier . This system will be used for seeding a powerful CPA laser chain.