Evidence of filamentation (self-focusing) of a laser beam propagating in a laser-produced aluminium plasma

Abstract

The thresholds for self-focusing (filamentation) of a laser beam in a laser-produced plasma have been computed for propagation of nanosecond duration pulses in short (<or=180 mu m thick), high-density (0.05-0.9 Ncr where Ncr is the critical density) multiply ionised absorbing plasmas. The authors also report results of an experimental study where they have observed filamentary structures in the X-ray emission from aluminium plasmas accompanied by an increase in the divergence of the light transmitted through them. Both observations indicate self-focusing has occurred at an intensity near to that predicted by the computer code, this being approximately=1013-1014 W cm-2 for nanosecond duration pulses in plasmas formed by irradiating light solids (Z<or=13).