Long-term stabilization of pulse-to-pulse energy of a high-energy multipass Ti:sapphire CPA system

Highly stable operation of a two-stage multipass Ti: sapphire amplifier (a four-pass pre-amplifier and a four-pass power amplifier) has been demonstrated in a 50-mJ-class chirped-pulse amplification system with 10-Hz repitition rate. By optimizing the ratio of pump energies to the two amplifiers and the optical losses artificially inserted into the second power amplifier, a short-term (50 seconds) fluctuation in pulse energy of less than 0.5% rms was achieved. In addition to the passive stabilization, an active stabilization system is equipped to correct slow-drift of the temporal average output energy, and a long-term (150 minutes) fluctuation of 0.7% rms was achieved.