Coupling between High-Frequency Plasma Waves in Laser-Plasma Interactions

Experimental evidence for the coupling between two electron plasma waves having nearly the same frequency but greatly differing in wave number is presented using time and wave-number resolved spectra of Thomson scattered light from the plasma. The qualitative features of the measured $w(t,k)$ spectra are predicted by a Lagrangian fluid description and reproduced in particle simulations. These show that the daughter waves generated in this mode coupling process take the energy preferentially from the large k wave without significantly affecting the small k plasma wave.