Directional Anisotropy of the Backward Four-Wave Mixing in Gases

Abstract

Directional anisotropy of the nonlinear polarization responsible for the backward four-wave mixing in gases has been theoretically investigated for Doppler broadened two-level and Raman type three-level systems. It has been found that definite separation of coherent and incoherent terms of the nonlinear polarization is possible via backward four-wave mixing and also that a single Lorentzian line shape is expected to be observed which enables us to unambiguously determine the relaxation rate of a dipole forbidden transition.