Electron Acceleration in Direct Laser-Solid Interactions Far Beyond the Ponderomotive Limit

摘要： In laser-solid interactions, electrons may be generated and subsequently accelerated to energies of the order of magnitude of the ponderomotive limit, with the underlying process dominated by direct laser acceleration. The breaking of this limit, realized here by a radially polarized laser pulse incident upon a wire target, can be associated with several novel effects. Three-dimensional particle-in-cell simulations show that a relativistic intense laser pulse can extract electrons from the wire and inject them into the accelerating field. Antidephasing, resulting from collective plasma effects, is shown here to enhance the accelerated electron energy by 2 orders of magnitude compared to the ponderomotive limit. It is demonstrated that ultrashort radially polarized pulses produce superponderomotive electrons more efficiently than pulses of the linear and circular polarization varieties.