Tailoring high amplitude plasma waves via autoresonant beat-wave excitation

Autoresonant excitation of plasma waves can be realized by using a chirped beat frequency of two driving lasers [R.R. Lindberg et al 2004 PRL 93, 055001]. The resulting robust and stable plasma waves can be controlled through the chirp, reaching amplitudes above the Rosenbluth limit [M.N. Rosenbluth and C.S. Liu 1972 PRL 29, 701] and allowing an optimization of the resulting electron acceleration. Going beyond previous studies using a cold electron fluid model, we revisit this scheme with particle-in-cell (PIC) simulations [M. Luo et al. 2024 Phys. Rev. Res. 6, 013338] to clearly identify its validity range. We push the description to a regime where previously overlooked fluid non-linearities, self-injection and kinetic effects become important. We show that frequency chirp allows efficient control of the wave amplitude and self-injection even in this new regime. We also explore multiple-dimensional effects impacting the transverse structure of the wakefield when strong electron acceleration is achieved. The analysis, supported by large scale 2D PIC simulations, shows that in spite of the reduction of spatial coherence, the acceleration of self-injected electrons remains at 70% to 80% of that observed in one dimension.