ELECTROMAGNETICALLY INDUCED TRANSPARENCY WITH COHERENT AND STOCHASTICFIELDS

This paper deals with electromagnetically induced transparency (EIT), i.e., a significant suppression of absorption at a material transition (in the form of a dip in an absorption spectrum), due to a strong las er field, coupling the excited level with an auxiliary excited (unpopu lated) level. A comprehensive theory of EIT is developed for the cases of coherent and Markovian phase-and amplitude-phase-fluctuating coupl ing fields. For a coherent coupling field, a shift of the absorption m inimum from the two-photon resonance is revealed in the off-resonance case. Two models of amplitude-phase fluctuating fields are considered: the chaotic field and the uncorrelated-jump field. Closed analytical expressions for EIT line shape are derived and exact Limits of differe nt regimes of EIT an obtained, the emphasis being on the near-resonanc e case, The main conclusion is that an amplitude-phase-fluctuating fie ld can induce significant transparency, though reduced in comparison t o a phase-fluctuating field of the same average intensity and bandwidt h. EIT decreases with the increase of the bandwidth for all stochastic models considered. EIT with a chaotic field is generally less pronoun ced than EIT with an uncorrelated-jump field of the same intensity and bandwidth, the difference increasing with the field intensity. The po ssibility of experimental verification of the results obtained is disc ussed.