Phase Dependence Of The Absorption And Dispersion Of The Trichromatically Driven Medium

Recently, atomic coherence or quantum interference effect has been the important work in quantum optics and laser physics. In this paper, we study deeply the trichromatic phase manipulation of the response of a two-level medium to an arbitrarily intense probe field via using optical semi-classical theory, and certain important results are obtained. Compared to the case of monochromatic excitation, polychromatic excitation has more important applications in resonance fluorescence and optics nonlinearity. Considering the fact that multiple switching from normal to anomalous dispersion at multiple frequency regimes has some potential uses in quantum computation and quantum information, etc, we explore mainly the dispersion switching properties of a two-level system driven by the trichromatic field.We adopt the double harmonic expansion method of density matrix element and investigate the phase dependence and independence of the response of a trichromat-ically driven two-level medium to an arbitrarily intense probe field. The sum of the relative phases of the sideband components of the trichromatic field compared to the central component plays a crucial role in the response of the medium. For a weak probe field, as the sum of the relative phases changes from 0 to π, multiple switching can be achieved, in which switching from normal to anomalous dispersion occurs in multiple separate frequency regimes. The switching from normal to anomalous dispersion, which corresponds to the switching from subluminal to superluminal light propagation, has recently been paid considerable attention. The remarkable dependence on the sum phase is also shown for a strong probe field. While, it is noticeable that the changes in the respective relative phases have no influence on the response of the medium when the sum of the two relative phases is fixed.