Simultaneous evolution of spot size and length of short laser pulses in a plasma channel

Nonlinear, nonparaxial propagation of an intense, short, Gaussian laser pulse in a preformed plasma channel having a parabolic radial density profile is analyzed. The variational technique is used to obtain equations describing the evolution of laser spot size and pulse length in the channel. Relativistic nonlinearity and group velocity dispersion effects have been taken into account and numerical methods are used to study the simultaneous evolution of the laser spot and pulse length