Mirrorless dispersive optical bistability due to cross trapping of counterpropagating beams in sodium vapor

We report the first observation to our knowledge of mirrorless optical bistability based on a dispersive effect, namely, cross-trapping optical bistability due to the mutual interaction of two counterpropagating beams. The phase conjugation of a probe beam generated by four-wave mixing in such a system is sensitive to the intensities of the counterpropagating beams and has been used to monitor the bistability.