  Cavity quantum electrodynamics (CQED) plays an elegant role of studying
strong coupling between light and matter. However, a non-mechanical, direct and
dynamical control of the used mirrors is still unavailable. Here we
theoretically investigate a novel type of dynamically controllable cavity
composed of two atomic mirrors. Based on the electromagnetically induced
transparency (EIT), the reflectance of atomic mirror is highly controllable
through its dispersive properties by varying the intensity of applied coupling
fields or the optical depth of atomic media. To demonstrate the uniqueness of
the present cavity, we further show the possibility of manipulating
vacuum-induced diffraction of a binary Bose-Einstein condensate (BEC) when
loading it into a dispersive cavity and experiencing superradiant scatterings.
Our results may provide a novel all-optical element for atom optics and shine
new light on controlling light-matter interaction.
