Observation of postsoliton expansion following laser propagation through an underdense plasma.

The expansion of electromagnetic postsolitons emerging from the interaction of a 30 ps, 3×10¹8 W cm⁻² laser pulse with an underdense deuterium plasma has been observed up to 100 ps after the pulse propagation, when large numbers of postsolitons were seen to remain in the plasma. The temporal evolution of the postsolitons has been accurately characterized with a high spatial and temporal resolution. The observed expansion is compared to analytical models and three-dimensional particle-in-cell results, revealing a polarization dependence of the postsoliton dynamics.