Raman scattering and excitation of the harmonics of intense laser radiation in cold plasmas

Plane linearly and circularly polarized intense electromagnetic waves in cold underdense plasmas are considered and approximate expressions for them and adiabatic relations between their local amplitudes and frequencies are established. A general three-dimensional theory is developed for the instability of propagation of a plane monochromatic circularly polarized electromagnetic wave in plasma including the violation of its initial polarization. Excitation of harmonics resulting from the relativistic and charge-displacement nonlinearities, scattering due to the response of the electron fluid, decay instability of harmonics leading to the emergence of scattered electromagnetic waves and plasmons, wave-wave interactions, and the generation of a continuum of scattered radiation are studied.