Two-Photon Absorption and Stimulated Raman Scattering on Excited Helium Atoms in a Plasma

Abstract

By focusing simultaneously microwave radiation and the beam from a tunable dye laser into a helium plasma, we observe two-photon absorption and stimulated Raman scattering on excited helium atoms. Both effects can be used to measure high-frequency electric fields in plasmas, and we discuss the advantages of this method as compared with the standard technique where such fields are investigated in emission spectra.