Plasma channel formation by short pulse laser

A short pulse laser propagating through a preformed plasma exerts a radial ponderomotive force on the electrons and creates a low density plasma channel via ambipolar diffusion. If the radial intensity profile of the laser beam is clamped, i.e., assumed Gaussian in r with fixed half-width r(0), then closed form analytic solution of the evolution of plasma density in the channel is obtained in the perturbation approximation, Delta n much less than n(0), where Delta n is the modification in electron density over its equilibrium value no, by solving the linearized equation of continuity. The relevance of the channel for low spot size beams self-focusing is examined. (C) 1996 American Institute of Physics.