  The nonlinear regime of laser-plasma interaction including both
two-plasmon--decay (TPD) and stimulated Raman scattering (SRS) instabilities
has been studied in three-dimensional (3-D) particle-in-cell simulations with
parameters relevant to the inertial confinement fusion (ICF) experiments. SRS
and TPD develop in the same region in plasmas, and the generation of fast
electrons can be described accurately with only the full model including both
SRS and TPD. The growth of instabilities in the linear stage is found to be in
good agreement with analytical theories. In the saturation stage the enhanced
low-frequency density perturbations driven by the daughter waves of the SRS
sidescattering can saturate the TPD and consequently inhibit the fast-electron
generation. The fast-electron flux in 3-D modeling is up to an order of
magnitude smaller than previously reported in 2-D TPD simulations, bringing it
close to the results of ICF experiments.
