Relativistic focusing and ponderomotive self-channeling of intense laser beams

Summary form only given, as follows. The ponderomotive force associated with an intense laser pulse in plasma expels electrons radially, leading to cavitation. Relativistic effects as well as cavitation modify the refractive index of the plasma. An envelope equation for the laser spot size is derived using the source dependent expansion method and reduced to quadrature. An analytical expression for the pseudo-potential is obtained for arbitrary laser amplitudes within the long-pulse, quasi-static limit. Matched beam solutions of the envelope equation are obtained. For normalized laser amplitudes |a| unity the analysis indicates a contraction of the laser spot size and a corresponding increase in the amplitude. Solutions of the envelope equation describing the approach to the matched beam solution starting from arbitrary initial conditions are presented. Electron cavitation and collapse of the laser beam envelope are also indicated in two-dimensional simulations in the large |a| regime.