Laser Excitation of Wakefields in a Parabolic Plasma Channel
  A Gaussian laser pulse with a square profile in time propagating in a parabolic plasma channel, exerts a ponderomotive force on electrons that drives a large amplitude electrostatic wake potential phi. An analytic solution for phi is possible when a characteristic relation is fulfilled. For pulse duration tau ~ 9 tau_p / 4, where tau_p is the plasma period, the plasma wake potential on the axis is twice the ponderomotive potential phi_0. 
R.Annou, V.K.Tripathi, R.K.Jarwal, A.K.Sharma