Electromagnetically induced absorption in four-level atomic system

A four-level atomic system is employed as an example, in which three transitions are in N configuration and the middle transition is used as a probe transition. We show that electromagnetically induced absorption and electromagnetically induced transparency can appear in the four-level N-type atomic system, which are dependent not only on the spontaneous transfer of atomic coherence, but also on the relaxation of the fourth level, the Rabi frequency of the coupling and the control field.