Diagnostic research of stimulated Raman back scattering in ultrashort-ultraintense laser interaction with gas target

The stimulated backward Raman scattering generated by femosecond laser interaction with gas target was measured. In the condition of experiment, the stimulated Raman backscatter(SRS) is in the strongly coupled mode, and several nonlinear Stokes satellite peaks appeare in the scattering spectrum. The frequency space of Stokes peaks is smaller than the plasma wave frequency. The plasma density range of laser interaction with gas target deduced from backward SRS is 5×1018 cm-3. These results are consistent with the prediction of a strongly coupled Raman theory．