Influence of atomic species on laser pulse propagation in underdense plasmas

A 65 fs, intense (similar to 10(18) Wcm(-2)) laser pulse incident on a supersonic, laminar gas-jet was investigated via 90 Thomson Scattering and interferometry diagnostics. In order to study the effect of atomic species on laser pulse propagation, the laser interaction with different gases (Nitrogen and Argon) was monitored. In the experimental conditions, both the atomic species resulted in similar electron densities, however, early diffraction of the laser pulse was observed in Argon gas, while, stable propagation of the pulse over several Rayleigh lengths was seen in the case of Nitrogen gas target. Features of the scattering region indicate a competition between optical diffraction and intensity dependent non-linear focusing of the pulse. The observations suggest that proper choice of the target is essential within the available laser pulse parameters, as it can enhance or spoil the propagation of laser pulse in plasmas. (C) 2011 Elsevier B.V. All rights reserved.