Circular dichroism of four-wave mixing in nonlinear metamaterials

Metamaterial engineering offers a route to combine unusual and interesting optical phenomena in ways that are rare or nonexistent in nature. As an exploration of this wide parameter space, we experimentally demonstrate strong cross-phase modulation and four-wave mixing in a chiral metamaterial, highlighting the interplay of nonlinearity and circular dichroism. Furthermore, we show that the magnitude of the nonlinear parametric interaction follows certain selection rules regarding the circular polarizations of the various interacting waves. Using a coupled-mode analysis and finite element simulations, we relate these selection rules to the metamaterial's internal symmetries as well as its circular dichroism in the linear regime. © 2013 American Physical Society.