Self-trapped laser beams in plasma

A moment theory for the nonlinear quasi-optical equation with saturation is applied to self-trapped laser beams in plasma for the ponderomotive nonlinearity. The results differ quantitatively from those obtained form the paraxial ray theory but do agree qualitatively in that there is a minimum beam radius of order c/ωp, a threshold ’’critical’’ power, no upper limit to the power that can be transmitted, and the self-trapped beams are stable.