Surface electron acceleration in relativistic laser-solid interactions

Under the grazing incidence of a relativistic intense laser pulse onto a solid target, two-dimensional particle-in-cell simulations show that intense quasistatic magnetic and electric fields are generated near the front target surface during the interaction. Some electrons are confined in these quasistatic fields and move along the target surface with betatron oscillations. When this oscillating frequency is close to the laser frequency in the particle frame, these electrons can be accelerated significantly in the reflected laser field, similar to the inverse free-electron-laser acceleration. An analytical model for this surface betatron acceleration is proposed.