Bistability behaviors in an optical ring cavity filled with a dense V-type four-level atomic medium are theoretically investigated.It is found that the optical bistability can appear in the negative refraction frequency band,while both the bistability and multi-stability can occur in the positive refraction frequency bands.Therefore,optical bistability can be realized from conventional material to negative index material due to quantum coherence in our scheme.
We study the spatial behavior of a deflected beam in a coherent A-type three-level atomic medium with an inhomogeneous control laser.When the Rabi coupling by the control laser is in a Gaussian profile,the spatialdependent refraction index of the atomic medium will result in a beam splitting as well as the deflection of the slow probe light under electromagnetically induced transparency.In terms of the phase difference between the two splitting beams and the position of the splitting,the possible interpretation of the splitting is given in theory.
