Nonlinear single-mode fiber coupler using liquid crystals

The operation of a new nonlinear optical waveguide coupler, fabricated in single-mode fibers and using a liquid crystal as the nonlinear medium, is described. Strongly intensity-dependent coupling and associated bistability are observed to occur in the intensities of the light in the uncoupled and coupled fibers, plotted as a function of the intensity in the input fiber. The effects of applying a dc electric field are also reported. Criteria for the development of liquid crystals suitable for the construction of various types of nonlinear optical devices in single-mode optical fibers are proposed.