A new nonlinear Raman instability in underdense plasma is investigated theoretically. Unlike the usual linear Raman instabilities which grow exponentially in time, this instability takes a finite amount of time to diverge. The explosion time t∞, depends on the initial level of the perturbation. A general set of equations for spatio-temporal evolution of the forward nonlinear Raman scattering is derived and its temporal evolution is studied in detail. This new instability results in the generation of forward Raman radiation shifted by half the plasma frequency for laser intensities of order or exceeding 1018 W/cm2, something that has been recently observed [A. Modena (private communication, 1995)].
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics