Saturation of Stimulated Backscattered Radiation in Laser Plasmas

Measurements of the back reflection from laser-produced plasmas have been carried out for laser intensities of up to 1.5\ifmmode\times\else\texttimes\fi{}${10}^{16}$ W/${\mathrm{cm}}^{2}$ with pulse durations of 120 psec using spherical low-$Z$ targets. The reflectivity of the plasma increases with incident intensity but saturates at a value of 10%. The intensity-dependent reflectivity is attributed to stimulated Brillouin scattering.