Near-surface electron acceleration during intense laser-solid interaction in the grazing incidence regime

When a relativistically intense p-polarized laser pulse is grazingly incident onto a planar solid-state target, a slightly superluminal field structure is formed near the target surface due to the incident and reflected waves superposition. This field structure can both extract the electrons from the target and accelerate them. It is theoretically shown that the acceleration is possible and stable for a wide range of electron initial conditions. PIC simulations confirm that this mechanism can actually take place for realistic parameters. As a result, the electron bunches with charge of tens of nC and GeV-level energy can be produced using a laser intensity $10^{21}-10^{22}$ W/cm${}^2$. It is also shown that the presence of a preplasma can increase the acceleration rate, which becomes possible because of more efficient electron injection into the accelerating field structure.