Hartman effect in one-dimensional photonic crystal doped by Λ-type three-level atoms

Hartman effect in one-dimensional photonic crystal with a defect layer doped by Λ-type three-level atoms is theoretically discussed. It is found that the phase time delay can be controlled from positive to negative (or vice versa) just by the intensity of coupling field. Furthermore, in the presence of quantum interference or an incoherent pump field the medium becomes completely phase dependent. Therefore, the phase time delay can be switched from negative to positive just by adjusting the relative phase of the applied fields and the rate of an incoherent pump field.