From self-focusing light beams to femtosecond laser pulse filamentation

2012 marked the 50th anniversary of the first published prediction of the self-focusing phenomenon in light beams. The recent revived interest in the subject is due to advances in high-power femtosecond laser technology and due to the possibility they provided of creating extended filaments of high light field intensity in gases and condensed media. This review shows in retrospect how our understanding of the self-action of light evolved from the self-focusing of laser beams in the 1960s to the filamentation of femtosecond laser pulses at present. We also describe the current status of this rapidly growing area of nonlinear optics and laser physics. Finally, we discuss, in general terms, what the phenomena of laser beam self-focusing and laser pulse filamentation have in common and how they differ.