A method for generating an ultrashort electron beam from a resonantly excited nonlinear wake field is proposed using a short laser pulse with a relativistic intensity. The considerable amount of electrons up to 10 ${\mathrm{C}/\mathrm{m}}^2$ are extracted from an appropriate thin plasma layer. When the laser intensity is highly relativistic, the electron beam is singly bunched and has a pulse length less than the laser wavelength and a large energy spread with a maximum energy of tens of MeV.

• Received 28 September 1998

DOI:https://doi.org/10.1103/PhysRevE.59.1263