Two laser beams traveling side by side in vacuum do not interact, irrespective of how closely they approach. In a nonlinear optical medium, however, light-light interactions are quite different, as evidenced by the self-focusing effect seen when an intense laser beam passes through such as medium. Theoretically, the self-focusing can be described by associating a potential well, induced by the nonlinearity, with the propagating laser beam. Ren et al. present a model that shows that one propagating laser beam can interact with and influence the trajectory of a second beam. Under appropriate conditions, their model calculations show that the attractive force between the two beams can result in them spiraling around each other. The results may have potential in future light-steering applications in which light may be directed with light. — ISO
Phys. Rev. Lett. 85, 2124 (2000).