Asymptotic wave-wave processes beyond cascading in quadratic nonlinear optical materials

Abstract
The method of multiple scales is used to derive several different systems of evolution equations for multiple interacting waves propagating in a strongly dispersive, weakly quadratically nonlinear optical material. Several two- and three-wave signaling problems are discussed. Among the problems discussed are the interaction between a low frequency field and the optical frequency field and between the optical frequency field and its second-harmonic field. In the efficient phase-matching regime, three-wave-mixing equations are obtained where quadratic nonlinearities dominate. Here, methods are discussed for cascading second-order nonlinearities to obtain intensity-dependent effects. For the large-phase-mismatch regime, cross-phase-modulation equations, analogous to fiber optics, are obtained where cubic nonlinearities dominate, and intensity-dependent modulations beyond cascading are obtained. Finally, the three-interacting (sum frequency) wave problem is examined for small and large asymptotic phase mismatch regimes. Analytical solutions to the derived evolution equations are given.

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