Output Energy Fluctuations of the Nd:YAG Amplifier Chain of a Photoinjector Drive Laser System

In the Etude d'un LaSer Accordable, electron bunches consist of trains of picosecond pulses extracted from a photocathode by a drive laser system: This system consists of a mode-locked Nd:YAG oscillator followed by a pulse compressor, an amplifier chain, and a second-harmonic-generation stage. The performance of the linac critically depends on the energy stability of this system. It is demonstrated theoretically and experimentally that the energy fluctuations of the Nd:YAG oscillator are significantly reduced by the amplifier chain, that the remaining energy fluctuations of the whole system are mainly due to amplifier pump fluctuations, and that the amplifier chain can be optimized to reduce the global energy fluctuations from 1.5% rms to <1% rms.