Observation of four-wave parametric interactions in cesium and barium vapors

Frequency-split (nondegenerate) four-wave quasiresonant interactions between monochromatic waves were observed in cesium vapor. The intensity of the generated waves was sufficient for cascade stimulated emission. Moreover, it was found that sum frequencies were generated in barium vapor and a conversion efficiency of ~ 10^–3 (measured relative to the pump energy) was sufficient for a quasiresonant four-wave parametric process.