Abstract
We propose a device whose reflectivity can be controlled optically over a wide frequency band. To this objective, we propose a Fabry-Perot cavity filled with a three-level atomic gas such that the effective susceptibility can be adjusted through incoherent pump and coherent driving fields. Adopting the concepts of electromagnetic-induced transparency and the white light cavity, we can control the susceptibility to break or satisfy the resonance condition over a wide frequency range, resulting in a wide-band optical switch. In addition to numerical calculation, we first give the analytical parameters, such as pump rate, and the Rabi frequency of the driven field, required for white light cavity in this paper. Using such a cavity as a wall of another cavity, we can, optically, realize a wide-band Q-switched cavity. Such a device can also be used as a new type of optical switch for quantum information.