Stimulated One-Photon and Multiphoton Processes in Strongly Driven Multilevel Atomic Systems

Abstract

We derive and discuss the behaviour of several multilevel atomic systems relevant to the problem of stimulated one-photon and multi- photon processes under the simultaneous action of strong laser fields and weak signal fields. The systems considered here consist of a single two-level atom, whose level degeneracies of the ground and excited states have been removed by internal process or by applying an external electric or magnetic field, respectively. In this system, one of the two ground state levels of the atom is a meta- stable one and its electron population is depleted through the action of either one laser field (three-level atom) or two laser fields (four-level atom), respectively. The strong laser fields deplete the metastable state by bringing the electrons into the excited states from where the electrons decay through the signal fields into the lower ground states of the system. For such systems, the fluorescent spectra of the signal field are described by the stimulated processes of one-photon, three-photon, and two-photon Raman, respectively. The dynamic aspects of such processes are discussed in detail. It is shown that the intensities of the sidebands for the processes in question take negative values indicating that a strong amplification of the signal field occurs at the corresponding frequencies. The computed spectra for the processes in question are presented graphically for different values of the Rabi frequencies and detunings. The derived results are discussed in detail and compared with the observed spectra.