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Two-Wave Mixing In Resonant Media

We have studied two-wave mixing in resonant media. Illumination with two beams of the same frequency leads to the formation of a spatially local volume grating with no exchange of energy between the writing beams, each beam merely reducing the absorption experienced by the other beam. Nondegenerate two-wave mixing leads to gain for one beam and additional absorption for the other beam as they propagate through the medium. Starting from first principles, the explicit forms of the two-beam coupling constants are derived using third-order perturbation theory, and their dependence on material and experimental factors is examined.