Interaction of highly relativistic short laser pulses with plasmas and nonlinear wake-field generation

Generation of nonlinear plasma oscillations by intense short laser pulses is considered. It is shown that longitudinal plasma waves with relativistic amplitudes and phase velocities close to the speed of light c can be excited in the wake of a strong single laser pulse in a cold plasma. Analytical as well as numerical studies of the relativistic wake-field generation by the laser pulses with realistic shapes are carried out. The nonlinear scheme of the laser wake-field accelerator is suggested. It is found that the maximum amplitude of the excited plasma waves is to be expected at the wave-phase velocities of less than c and not at those approximately equal to c. A second laser pulse sent after the first one is considered, and this trailing pulse can both amplify and 'absorb' the wake-field created by the first laser pulse. Applications of the results to the proposed Livermore High-Brightness Lasers are discussed. (Author)