Coupling between electron plasma waves in laser-plasma interactions

A Lagrangian fluid model (cold plasma, fixed ions) is developed for analyzing the coupling between electron plasma waves. This model shows that a small wave number electron plasma wave (omega(2),k(2)) will strongly affect a large wave number electron plasma wave (omega(1),k(1)), transferring its energy into daughter waves or sidebands at (omega(1)+n omega(2),k(1)+nk(2)) in the lab frame. The accuracy of the model is checked via particle-in-cell simulations, which confirm that the energy in the mode at (omega(1),k(1)) can be completely transferred to the sidebands at (omega(1)+n omega(2),k(1)+nk(2)) by the presence of the electron plasma mode at (omega(2),k(2)). Conclusive experimental evidence for the generation of daughter waves via this coupling is then presented using time- and wave number-resolved spectra of the light from a probe laser coherently Thomson scattered by the electron plasma waves generated by the interaction of a two-frequency CO2 laser with a plasma. (C) 1996 American Institute of Physics.