Controlled shift of optical bistability hysteresis curve and storage of optical signals in a four-level atomic system

The controllable shift of optical bistability (OB) hysteresis curve in a four-level atomic system of ⁸⁷Rb inside an optical ring cavity was analyzed. Investigations show that the atomic system operated at near conditions of coherent population trapping due to atomic coherence. It was found that the refractive and absorptive χ⁽³⁾ nonlinearities were enhanced by the atomic coherence provided the physical mechanism of the phenomena. The results show that OB system could be used in all-optical switches, information storage and logic circuits of all-optical information processing.