Nonabsorbing atomic coherences by coherent two-photon transitions in a three-level optical pumping

An investigation is conducted of optical pumping phenomena in the case of laser irradiation. An atomic system with two ground-state levels and one excited level is considered. The system is irradiated by a light beam containing two coherent modes, each of which is resonant with one of the coupled transitions. The reported analysis is based on the solution of Bloch-like equations of motion for the three-level system in close analogy to the standard two-level case. Analytical expressions for the excited-state populations and the optical coherences are obtained.