Optical switching and bistability in a degenerated two-level atomic medium under an external magnetic field.

We propose a simple system for both optical switching and bistability based on degenerated two-level atoms placed in a ring cavity and an external magnetic field. The magnetic field splits a lower level into two separated levels, both of which are connected to an upper level by coupling and probe laser fields. Under an electromagnetically induced transparency regime, the system exhibits optical bistability and switching properties in which its thresholds and switching rate can be controlled by modulating intensity of the magnetic field or the coupling light field. Furthermore, the system can be controlled to work in varying frequency regimes by using a sole laser for both coupling and probe fields. Such a proposed scheme may be useful for realization of optical switches and storage devices.