Two-photon interaction of coherent radiation with a thin film of resonant atoms

The problem of the interaction of an ultrashort optical pulse and a thin fi lm of resonant atoms under the conditions of two-photon absorption, third-h armonic generation, and the inverse effect of the latter on the pump pulse via Raman scattering is studied. The fact that the field acting on an atom differs from the macroscopic field in the film is also taken into considera tion. It is shown that the polarization of the film undergoes dynamic relax ation even in the absence of irreversible relaxation, suppressing Rabi osci llations and establishing stationary values of the populations of the reson ant energy levels and of the polarization of the film at the pump and the t hird-harmonic frequencies. (C) 1999 American Institute of Physics. [S1063-7 761(99)00301-7].