Pressure-Induced Extra Resonances in Four-Wave Mixing

Abstract

The first observation of pressure-induced extra resonant enhancements of a coherent four-wave---mixing signal is reported. When the difference between two input frequencies, ${\ensuremath{\omega}}_{1}$ and ${\ensuremath{\omega}}_{2}$, corresponds to the separation of two unpopulated upper levels, a resonant enhancement of the generated intensity at $2{\ensuremath{\omega}}_{1}\ensuremath{-}{\ensuremath{\omega}}_{2}$ is caused by collisions.