Experimental Demonstration of Relativistic Self-Channeling of a Multiterawatt Laser Pulse in an Underdense Plasma

We report the first clear experimental demonstration of relativistic self-channeling of a multiterawatt laser pulse interacting with an underdense plasma. We show via Thomson scattering observations that for laser power above the critical power for self-focusing the beam remains trapped and guided over the plasma length. These observations are in fairly good agreement with a numerical model describing the laser propagation and taking into account the plasma response to the ponderomotive force.