The influence of a second resonance on the saturation characteristics of the four-wave sum mixing

Experimental results are presented, related to the saturation mechanisms of the four-wave sum mixing (4-WSM) generation in Hg when a double resonance enhancement is employed, that is, a two photon resonance to the /spl delta//sup 1/S/sub 0/ state followed by the /spl delta//sup 1/S/sub 0/-6p'/sup 3/D/sub 1/ one photon coupling. This coupling is shown to alter the saturation characteristics of the four-wave sum mixing radiation by affecting the two-photon excitation to the /spl delta//sup 1/S/sub 0/ state, reduce the ionization of the Hg atoms by the incoming radiation and create an absorption window for the generated radiation in a region near the autoionizing state by modifying the linear susceptibility.<
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