Second-harmonic generation of laser radiation in a plasma with a density ripple

High-power laser radiation with frequency omega /sub 1/ and wave vector k/sub 1/z propagating through a plasma at an angle to a density ripple (0,k/sub 0/) produces current and density perturbation at ( omega /sub 1/,k/sub 1/+k/sub 0/). The density perturbation couples with the oscillatory velocity at ( omega /sub 1/,k/sub 1/) to produce nonlinear current at (2 omega /sub 1/, (2k/sub 1/+k/sub 0/)) driving second-harmonic electromagnetic radiation. For a specific value of ripple wave number k/sub 0/=k/sub 0c/, the phase-matching conditions for the second-harmonic process are satisfied, leading to resonant enhancement in the efficiency of energy conversion, k/sub 0c/ decreases with the frequency omega /sub 1/ of the laser.>