Attosecond pulse generation in the relativistic regime of the laser-foil interaction: The sliding mirror model

Theory of the attosecond pulse generation during the interaction of a short relativistic-irradiance laser pulse with a thin overdense plasma slab is developed. The nonlinear electric current caused by the electron motion at relativistic velocity generates the high-order harmonics of the incident radiation. These harmonics are phase locked and can produce pulses with attosecond duration after spectral filtering. Conditions for the most efficient generation of single-attosecond pulses are discussed. A very efficient regime of attosecond pulse train generation without spectral filtering is proposed. The results are verified by the particle-in-cell simulations.