Transverse optical patterns for ultra-low-light-level all-optical switching

We review recent theoretical and experimental efforts toward developing an all-optical switch based on transverse optical patterns. Transverse optical patterns are formed when counterpropagating laser beams interact with a nonlinear medium. A perturbation, in the form of a weak switch beam injected into the nonlinear medium, controls the orientation of the generated patterns. Each state of the pattern orientation is associated with a state of the switch. That is, information is stored in the orientation state. A realization of this switch using a warm rubidium vapor shows that it can be actuated by as few as 600 40 photons with a response time of 5 μs. Models of nonlinear optical interactions in semiconductor quantum wells and microresonators suggest these systems are also suitable for use as fast all-optical switches using this same conceptual design, albeit at higher switching powers. A pair of counterpropagating beams induce an instability that generates transverse optical patterns. (A) Two spots form the unperturbed far-field pattern. (B) A weak beam incident at an angle to the pump beam axis causes the generated pattern to