Tunable slow and fast light in an atom-assisted optomechanical system with a mechanical pump

We theoretically investigate the optical response of an atom-assisted optomechanical system to a weak probe field at the presence of a strong coupling field and a time-dependent mechanical pump. We show that the phenomenon of optomechanically induced transparency can be converted to that of perfect absorption due to Jaynes-Cummings (J-C) coupling between a single-mode cavity field and a two-level atom, and the probe transmission strength can be further enhanced or suppressed by tuning amplitude and phase of the mechanical pump. Furthermore, phase dispersion of the transmission optical field is modified by controlling the J-C coupling strength and the applied pump, which provides an approach to tune group delay of the output probe field. Based on this hybrid optomechanical system, we can realize a conversion between slow and fast light effect by adjusting the J-C coupling strength. Moreover, the amplitude and phase of the mechanical pump as well as the coupling field amplitude can also be used to control the group delay. These results provide us an approach to manipulate light propagation, which will be helpful for quantum information processing.