Polarization- and Chirp-Controlled Beam Structure Engineering for Efficient Laser Electron Acceleration

This paper presents a comprehensive numerical study of vacuum electron acceleration driven by Hermite–cosh–Gaussian (HcG) laser pulses, emphasizing beam structure engineering as a route to enhance the efficiency and scalability of direct laser acceleration (DLA). The combined influence of the Hermite index (s), cosh–Gaussian decentered parameter (b), linear chirp parameter (C), and polarization state is systematically analyzed. The simulations reveal three distinct acceleration stages governed by a phase synchronization process, with the quasi-static phase identified as the regime of maximal energy transfer. Importantly, it is demonstrated that an optimally tailored linear chirp can dramatically enhance energy gain, while tuning the paramet,er b leads to improved field localization and extended synchronism, yielding peak energies up to ~8 "GeV" . A decisive role of polarization is revealed: circular polarization not only maximizes energy transfer but also suppresses sensitivity to the initial phase, thereby ensuring stable and reproducible acceleration. Furthermore, higher-order HcG modes are shown to expand the effective injection window, allowing even off-axis electrons to reach substantial energies. These findings demonstrate that chirped HcG beams, through polarization- and chirp-controlled beam structure engineering, offer a versatile and efficient driver for compact next-generation laser-based accelerators.