On the validity of the paraxial approximation for electron acceleration with radially polarized laser beams

摘要

In the study of laser-driven electron acceleration, it has become customaryto work within the framework of paraxial wave optics. Using an exact solutionto the Helmholtz equation as well as its paraxial counterpart, we performnumerical simulations of electron acceleration with a high-power TM01 beam. Forbeam waist sizes at which the paraxial approximation was previously recognizedvalid, we highlight significant differences in the angular divergence andenergy distribution of the electron bunches produced by the exact and theparaxial solutions. Our results demonstrate that extra care has to be takenwhen working under the paraxial approximation in the context of electronacceleration with radially polarized laser beams.