GENERATION OF LARGE-AMPLITUDE PLASMA WAKEFIELDS WITH LOW PHASE VELOCITIES BY AN INTENSE SHORT LASER-PULSE

The generation of nonlinear plasma waves with arbitrary phase velocities by an intense laser pulse is considered in order to determine the dependence of the maximum amplitude of driven waves on the group velocity of the laser pulse (or the phase velocity of excited wakefields). Analytical as well as numerical studies of the problem are carried out within the so-called quasi-static approximation. In the case of square-shaped laser pulses the analytical expression for the maximum amplitude as a function of the pump amplitude and the phase velocity is derived. The numerical analysis in the case of Gaussian pulses confirms the result that follows from the analytical formula: the lower the phase velocity of the wakefield, the greater is its maximum amplitude for a given amplitude of the driving pulse.