Polarization effects in the interaction between light and multilevel quantum systems

We develop a theory that describes the interaction of radiation and multile vel particles on the basis of the classical description of the orientation of angular momentum. For examples of application of this theory we take the problems of stimulated Raman scattering and of parametric generation of li ght in four-wave mixing. We find that the efficiency of the radiation proce sses largely depends on the polarization of the pump waves and on the types of optical transitions (Delta J) and to a much lesser extent on the value of the angular momentum J. We also explain some polarization phenomena obse rved in experiments on four-wave mixing. (C) 1999 American Institute of Phy sics. [S1063-7761(99)00608-3].