Nearly degenerate four-wave mixing enhanced by the ac Stark effect

A model is developed to describe nondegenerate four-wave mixing in a medium characterized by a single strong atomic resonance. The nonlinear response is calculated using the density-matrix formalism, and propagation effects are included by solving coupled-wave equations. This model predicts large resonant responses for signals detuned from the pump frequency by approximately the generalized Rabi frequency. Potential applications of the effects predicted by this model include construction of tunable bandpass filters and four-wave parametric oscillators.