Two copropagating lasers, having frequency difference Δω≈ωp, drive a plasma wave. The plasma beat wave amplitude increases with time initially due to the laser beams. As time grows, the plasma beat wave acquires large amplitude and it becomes susceptible to oscillating two-stream instability producing shorter wavelength Langmuir wave sidebands and a low frequency electrostatic mode. The decayed sidebands divert the energy of plasma beat wave by oscillating two-stream instability and saturate it.

A plasma-filled slow wave device, e.g., a backward wave oscillator (BWO), offers high efficiency for the generation of TM waves around 10 GHz, by a relativistic electron beam. A large-amplitude TM mode can parametrically drive a millimeter wave unstable by coupling it to a negative energy beam space charge mode. The frequency of radiation is maximum when it propagates in the TM01 mode. In the Raman regime of operation the growth rate of instability scales directly as one-fourth power of beam density and inversely as 21/4 power of relativistic gamma factor. The nonlocal effects reduce the growth rate.

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In a strongly magnetized nonisothermal plasma, a large amplitude electromagnetic wave propagating at an angle θ0 to a strong magnetic field undergoes stimulated Brillouin scattering off the ion mode. In an isothermal plasma the process goes over to stimulated Compton scattering with considerably lower growth rate. In both cases the growth rate is sensitive to the angle θ=(θ1−θ0), where θ0 is the angle of the pump wave vector k0 with the dc magnetic field, Bsẑ, and θ1 is the angle of the sideband wave vector k1 with Bsẑ.

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