Research on pulse energy stability in multi-pass amplifiers of CPA systems

Energy stability in multi-pass chirped-pulse amplification (CPA) amplifiers is critical for precision applications such as laser wakefield acceleration. This study employs theoretical and numerical methods to analyze the impact of seed and pump-source energy jitter on output stability. Perturbation analysis and Monte-Carlo simulations confirm that in the saturation regime, pump-source jitter dominates the output instability of a multi-pass amplifier. A dual stabilization strategy is therefore proposed and experimentally validated: the total pump fluctuation is reduced by a factor of 1/n through the statistical averaging of multiple independent pump sources, while the saturation operation further suppresses residual jitter propagation. Experiments on a 200 TW Ti:sapphire system demonstrate the effectiveness of both approaches. Under similar saturation levels, a four-pump configuration yields lower output jitter than a two-pump setup, and stronger saturation significantly improves stability for the same number of pumps. This work provides a clear and predictive framework for designing high-stability CPA drivers for advanced applications.