Atomic oxygen detection using two-photon degenerate four wave mixing

We report a new application of Forward Degenerate Four Wave Mixing to the two-photon transition 2p → 3p of atomic oxygen. This spectroscopy has been used to detect oxygen atoms produced in a microwave discharge. The possibility to determine number densities over a range of microwave plasma parameters is investigated. In contrast to conventional linear techniques, quantitative data are relatively easy to obtain even for environments with high background luminosity, limited optical access and inhomogeneous quenching.