Ultranarrow beams of electromagnetic radiation in media with a Kerr nonlinearity

The vector structure of a self-channeling electromagnetic field is determin ed by solving the complete system of Maxwell's equations in a transparent m edium with a Kerr nonlinearity. Self-channelling with an asymmetric angular distribution of the field occurs at powers several times the critical self -focusing power. As the power is increased, a universal (self-similar) fiel d structure develops in which only the scales change as the power is varied . Self-channelling with a channel width much smaller than the (linear) wave length of the light, i.e., a "needle of light" with an extreme concentratio n of radiant power, is found to occur. (C) 1999 American Institute of Physi cs. [S1063- 7761(99)00708-8].