Controllable Bistability and Normal Mode Splitting in an Optomechanical System Assisted by an Atomic Ensemble

We consider a system consisting of a standard optomechanical cavity and a trapped atomic ensemble. In such a system, we mainly focus on the features of optomechanical bistability and normal mode splitting with the presence of atomic ensemble. The results show that the energy of laser directly coupling the atomic ensemble can be enhanced effectively, and using this laser is more convenient and easier to realize the bistability and normal mode splitting than the traditional means. Besides, we find that atom-cavity field detuning also has a significant impact on optomechanical bistability, which offers us an important method to adjust and control the cavity mean photon number. At last, the numerical results show that atom-cavity field detuning and atom-cavity field coupling strength have an opposite effect on the normal mode splitting because they have different contributions to the effective cavity field decay rate.