Physicists at the University of Arkansas in Fayetteville have created an all-optical switch using electromagnetically induced transparency in an optical ring cavity. The technique, which they reported at the 2002 Quantum Electronics and Laser Science Conference in Long Beach, Calif., in May, promises applications in telecommunications and in optical computing.

In electromagnetically induced transparency, which researchers have employed to "stop" light, a medium illuminated with one laser beam tuned to an atomic transition permits the passage of a weaker beam tuned to another transition. For the experiments, the group stimulates or suppresses the nonlinear index of refraction of the rubidium gas by tuning and detuning the stronger beam, thereby changing the intensity of the cavity output by a factor of 30.