Research on the pre-pulses caused by post-pulses in the optical parametric chirped-pulse amplifier

Pre-pulses caused by the post-pulses in the optical parametric chirped-pulse amplifier were comprehensively studied for the first time, including the underlying mechanism for the delay-shift of pre-pulses, the intensity variation of pre-pulses affected by the initial delay of post-pulses and the pump energy, and also the nonlinear beat noise. The simulation and measurement confirmed that the high-order dispersion of the pulse stretcher was the main cause for the delay-shift of pre-pulses, which should be similar with the chirped-pulse amplifiers. The intensity of pre-pulses would decrease significantly as the initial delay of post-pulses increased, but would increase with the growth of pump energy. Moreover, the temporal position of the nonlinear beat noise in the experiment was successfully predicted by our simulation. This work could help us better understand the pre-pulses in OPCPA and provide helpful guidance for designing high-contrast laser systems.