Two-Dimensional Regimes of Self-Focusing, Wake Field Generation, and Induced Focusing of a Short Intense Laser Pulse in an Underdense Plasma

The results of a two-dimensional particle-in-cell simulation and of an analytical description of the propagation in an underdense plasma of a short, relativistically intense, laser pulse are presented. Self-focusing is proven in an ultrarelativistic regime for moderately long pulses. Pulses shorter than the plasma wavelength, but wider than it, excite a wake wave with a regular electric field. The electron density in the wake has a "horseshoe" shape and focuses a long pulse locally. The excitation of stimulated Raman backward scattering is observed.