Both long-lived coherences and coherent population oscillations result in dramatic enhancement of a Kerr nonlinearity in atomic media at very low intensity of resonant light. We demonstrate the possibility of separating the contributions from these effects under certain experimental conditions. We report a study of the nonlinear optical properties of atomic media under a variety of experimental conditions at low light intensity, paying particular attention to self-focussing, diffraction and quasi-degenerate wave mixing.

© 2007 Optical Society of America

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