Relativistic self-focusing in underdense plasma

We present the description of powerful beam self-focusing in underdense pla sma. The importance of electron cavitation, i.e. total electron evacuation under the effect of ponderomotive forces, is emphasized. Cavitation results in suppression of filamentation and the possibility to channel power well above the nominal critical power of self-focusing for a distance of many Ra yleigh lengths. (C) 2001 Elsevier Science B.V. All rights reserved.