Self-trapping of intense optical beams in plasmas

Two new results concerning the propagation of intense optical beams in plasmas are presented. The first is an analytic solution of the relativistic nonlinear equations governing the steady-state diffraction of intense, circularly polarized, electromagnetic beams in warm, quasi-neutral plasmas. The beams cannot self-focus, but can self-trap (propagate without diverging) at powers above P/sub c/=2 x 105 (lambda/sub D//lambda)2 MW, where lambda/sub D//lambda is the Debye length/vacuum optical wavelength ratio. The second result is an exact solution of the relativistic nonlinear equations for a self-trapped beam propagating with constant cross section; this solution yields self-consistent density and intensity profiles and a relativistic beam-plasma dispersion relation