Degenerate four-wave mixing in plasmas

We report an analysis of degenerate four-wave mixing in uniform plasmas and show that the magnitude of the third-order susceptibility (varying as lambda(2)) can be comparable to (10(-11) esu for lambda = 10.6 microm) or orders of magnitude larger (10(-3) esu for lambda= 10 cm) than the corresponding susceptibility in typical nonlinear materials. The nonlinear contribution to the macroscopic current resulting from the ponderomotive force is generated from the two-component fluid model by means of a linearized perturbation scheme. Numerical estimates of the nonlinear susceptibility show that relatively large signals can be produced easily without significant problems from competing physical phenomena such as self-focusing or stimulated Brillouin and Raman scattering.