  When a laser passes through underdense plasmas, Raman and Brillouin
Backscattering can reflect a substantial portion of the incident laser energy.
This is a major loss mechanism, for example, in employing lasers in inertial
confinement fusion. However, by slow rotation of the incident linear
polarization, the overall reflectivity can be reduced significantly. Particle
in cell simulations show that, for parameters similar to those of indirect
drive fusion experiments, polarization rotation reduces the reflectivity by a
factor of $5$. A general, fluid-model based, analytical estimation for the
reflectivity reduction agrees with simulations. However, in identifying the
source of the backscatter reduction, it is difficult to disentangle the
rotating polarization from the frequency separation based approach used to
engineer the beam's polarization. Although the backscatter reduction arises
similarly to other approaches that employ frequency separation, in the case
here, the intensity remains constant in time.
