Six-Wave Forward Scattering of Short-Pulse Laser Light at Relativistic Intensities

Forward scattering of short linearly polarized laser pulses in underdense plasma at relativistic intensities is examined. The linear polarization gives rise to a six-wave hybrid of the Raman forward scattering and relativistic modulational instabilities. Destructive interference between fluctuations in electron density and relativistic mass through the intervention of two high-frequency electrostatic modes decouples higher-order harmonics. This allows simple spacetime and spectral laser-pulse rest-frame models to be derived which are valid for arbitrarily high-laser intensities.