We report, we believe for the first time, expertmental demonstration of phase conjugation via degenerate four-wave mixing (DFWM) in a colllsional plasma. In such plasmas there are two dominant mechanisms that can generate the plasma density grating necessary for DFWM. These are the pon- deromotive forces resulting from the beating of each of the two pump waves with the probe1 wave and the thermal force resulting from localized colli- sional heating.2 It has recently been predicted that in plasmas where the collision mean free path is shorter than the grating wavelength, the contribution to the signal reflectivity due to the thermal force can be greater than that due to the pondero- motive force. In our experiments this is indeed found to be the case.
© 1989 Optical Society of AmericaPDF Article