COUPLING BETWEEN ELECTRON-PLASMA WAVES IN LASER-PLASMA INTERACTIONS

A Lagrangian fluid model (cold plasma, fixed ions) is developed for an alyzing the coupling between electron plasma waves. This model shows t hat a small wave number electron plasma wave (omega(2),k(2)) will stro ngly 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 energ y 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 e lectron plasma mode at (omega(2),k(2)). Conclusive experimental eviden ce for the generation of daughter waves via this coupling is then pres ented 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 plas ma. (C) 1996 American Institute of Physics.