Dynamic optical bistability in resonantly enhanced Raman generation
  We report observations of novel dynamic behavior in resonantly-enhanced stimulated Raman scattering in Rb vapor. In particular, we demonstrate a dynamic hysteresis of the Raman scattered optical field in response to changes of the drive laser field intensity and/or frequency. This effect may be described as a dynamic form of optical bistability resulting from the formation and decay of atomic coherence. We have applied this phenomenon to the realization of an all-optical switch. 
I. Novikova, A.S. Zibrov, D.F. Phillips, A. Andre and R.L. Walsworth