Optical hole-burnings and slow light in atoms vapors with laser interaction

Five coherent hole-burning can be simultaneously observed in the absorption spectra of four-level N-style atoms vapors. In this system they adopt a saturated laser co-propagates and two coupling lasers counter-propagate with a probe laser, and the saturated laser can not be in the destructive Doppler state with the probe light. The positions of the coherent hole-burning can be explained by Dressed-state theory. The middle narrow deep hole-burning is induced by the superposition of two coherent hole-burnings. The depth of the coherent hole-burning can be changed by adjusting the reference parameters and the Rabi frequency of the saturated laser. The positions of the coherent hole-burning can be changed by modulating the Rabi frequency of the probe light. By numerical simulation it is found that Rabi frequency of the saturated light plays an important role in slowing the propagating speed. These results may be useful in optical quantum memory and optical quantum information.