Femtosecond laser pulse generation by a stimulated Raman backscattering in a foil target

Ultra-short laser pulse can be generated by a stimulated Raman backscattering in a thin foil target. In an underdense exploding foil plasma, above an absolute instability threshold, Raman backscatter grows fast to saturate by strong quasiperiodic pulsations. When the laser intensity is of the order of 10(17)W/cm(2) and higher, exploding plasma is rapidly heated up to temperatures of a few keV to halt the instability, producing a coherent laser pulse of 20 fs or shorter in duration. The proposed scheme and the scaling are demonstrated by the coupled mode and relativistic particle simulations.