Broadband laser-driven electromagnetically induced transparency in three-level systems with a double Fano continuum

Abstract

We discuss the electromagnetically induced transparency (EIT) phenomenon for a model in which a structured continuum is described by a so-called double Fano structure; instead of one autoionizing (AI) state, two such states are embedded in a flat continuum. Such a Fano structure is the upper level of a Λ-like three-level system and is coupled to two lower ones by an external laser field involving δ-correlated, Gaussian, Markov process (white noise), simulating realistic conditions of the experiment. For such a system we derived and solved a set of coupled stochastic integrodifferential equations in the stationary regime, obtaining exact formulas determining the electric susceptibility of the system. Dispersion and absorption spectra of the medium susceptibility were calculated and compared with those already discussed in the literature. We have shown that the presence of an additional AI level considerably changes the structure of transparency windows and how noisy excitation influences the EIT processes.