Nonlinear interaction of ultra-intense laser pulses with a thin foil

The nonlinear interaction of an ultraintense laser pulse with a thin foil modifies the shape, the frequency content and the polarization of the pulse. An analytical description of this interaction is presented, together with the results of 1D3V and 2D3V particle in cell simulations. The conditions for the relativistic transparency of a thin foil are given and are shown to lead to the sharpening of the laser pulse. Such a pulse shape is advantageous for Laser Plasma Wakefield Acceleration of charged particles. In addition it is shown that a thin foil makes it possible to extract the accelerated particles nonadiabatically in the case of laser particle acceleration in vacuum.