RELATIVISTIC 2-PLASMON EXCITATION BY A LASER NEAR THE CRITICAL LAYER IN A PLASMA

An intense laser incident on a plasma relativistically modulates the e lectron mass at the second harmonic. Near the critical layer, the osci llatory mass couples two oppositely propagating Langmuir waves which g row at a rate Gamma similar to w(p)v(0)(2)/16c(2), where w(p) is the p lasma frequency, upsilon(o) is the oscillatory electron velocity and c is the velocity of light in vacuum. The decay is accompanied by the e xcitation of a low-frequency mode which at large wave number (kc > w(p )) enhances the growth rate of the two-plasmon process.