Observation of Energy Transfer between Frequency-Mismatched Laser Beams in a Large-Scale Plasma

The observation of energy transfer between two frequency-mismatched laser beams crossing in a low-density, large-scale plasma is described. The beams cross at an angle of 53° from parallel, with the average intensity in the blue beam equal to $2\times {10}^{15}$ W/c${\mathrm{m}}^2$. A redshifted probe beam is amplified by interaction with the blue beam and a stimulated ion acoustic wave. Significant energy is transferred to the probe when the difference in the frequencies of the two beams is comparable to the frequency of the acoustic wave. As much as 52% of the pump energy is transferred to the probe.