A four-wave difference mixing signal has been observed for what is, to our knowledge, the first time, in sodium in a methane-air flame. The experimental conditions used to observe the signal in the flame are reported. An explanation of the observed signal in terms of near two photon resonant difference four-wave mixing is proposed.
© 1992 Optical Society of America
J. P. Singh and F. Y. Yueh, "Four-wave difference mixing in Na in a CH4—air flame," Appl. Opt. 31, 4922-4925 (1992)