Coupling between electron and ion waves in Nd‐laser beat‐wave experiments

The beating between two colinear Nd‐YLF and Nd‐YAG lasers in a homogeneous plasma generates intense relativistic plasma waves associated with a high longitudinal electric field of the order of 1 GV/m. It is shown that these electron waves couple with ion waves in the regime of modulational instability. Electric field amplitude and saturation time obtained by Thomson scattering are in agreement with theoretical predictions taking this mechanism into account.