Backward and forward stimulated Raman scattering from thin foil targets with a 0.26 μm laser

Time-resolved spectra of backward and forward stimulated Raman scattering were measured from the interaction of 0.26 μm laser radiation with foil targets. The plastic foil targets were designed to go underdense before the peak of the 450 psec, 2×1015 W/cm2 laser pulse. The Raman spectra were quite narrow at any one time (Δω/ω∼0.05) and shifted to shorter wavelengths during the pulse. The backward Raman spectra can be well predicted by assuming that the Raman occurs in a disk-shaped region on the top of the parabolic density profile, using well accepted threshold estimates.