Threshold and saturation of the parametric decay instability

Observation of the time development of parametric instability reveals new oscillatory saturation states, whose frequency is proportional to the pump intensity. The self-consistent pump field simultaneously exhibits similar but 180° out-of-phase oscillations. Application of a small auxiliary driver wave ($E_t~0.1E_0$) at the electron sideband lowers the threshold and dramatically enhances the intensity of excited ion wave. Growth rate and functional dependence of threshold on ion damping are verified.