Weakly relativistic and ponderomotive effects on self-focusing and self-compression of laser pulses in near critical plasmas

The spatiotemporal dynamics of high power laser pulses in near critical plasmas are studied taking in to account the effects of relativistic and ponderomotive nonlinearities. First, within one-dimensional analysis, the effects of initial parameters such as laser intensity, plasma density, and plasma electron temperature on the self-compression mechanism are discussed. The results illustrate that the ponderomotive nonlinearity obstructs the relativistic self-compression above a certain intensity value. Moreover, the results indicate the existence of the turning point temperature in which the compression process has its strongest strength. Next, the three-dimensional analysis of laser pulse propagation is investigated by coupling the self-focusing equation with the self-compression one. It is shown that in contrast to the case in which the only relativistic nonlinearity is considered, in the presence of ponderomotive nonlinearity, the self-compression mechanism obstructs the self-focusing and leads to an increase of the laser spot size.