RELATIVISTIC SELF-FOCUSING OF AN ULTRA-INTENSE LASER-PULSE IN A PLASMA

New compact multiterawatt lasers allow us to study the relativistic regime of laser-plasma interaction. The propagation of a multiterawatt subpicosecond laser pulse in a plasma has been investigated theoretically and experimentally. A 10 TW laser pulse at a 1064 nm wavelength has been focused in a hydrogen gas jet. Thomson scattering observations show that a relativistic self-focusing and channeling occur when the laser power exceeds a critical value predicted by theory. The amount of enhancement in self-focused intensity exceeds one order of magnitude. The laser pulse propagates through the plasma over a distance much larger than the Rayleigh length determined by vacuum diffraction.