Multiple photon transitions induced by a dichromatic laser field

Abstract

Three-photon transitions induced by a dichromatic C${\mathrm{O}}_{2}$ laser operating on the $P(10)$ and $P(20)$ lines of the 961-${\mathrm{cm}}^{\ensuremath{-}1}$ band have been observed in a helium plasma. Laser photons interact resonantly with the $4^{3}S$ and $4^{3}P$ helium levels, resulting in new spectral lines which flank the 4713-\AA{}, $2^{3}P\ensuremath{-}4^{3}S$ He line. The multiple photon transition rates are calculated from a numerical diagonalization of the interaction Hamiltonian and are shown to be in agreement with experimental results.