Abstract
Controlling reflectivity optically over a wide range of frequency band can be of great demand technologically. In this paper we show how this can be realized using a Fabry-Perot cavity filled with a three-level atomic gas. Furthermore, we employ both concepts of electromagnetic induced transparency EIT and the white light cavity which in turn play the essential rule to control the susceptibility of the atomic gas. Once the susceptibility is controlled, all one needs to do is to look for the satisfying resonance conditions that run over a wide range of frequencies, which results in a wide band optical switch.