Efficient energy transfer between four-wave-mixing and six-wave-mixing processes via atomic coherence

We demonstrate efficient energy exchange during propagation between four-wave-mixing FWM and sixwave-mixing SWM signals generated in a four-level inverted-Y atomic system, which fall in the electromagnetically induced transparency window. After an initial growth distance for both FWM and SWM fields in the atomic medium, these two nonlinear optical processes compete and exchange energy between them, and eventually reach their respective steady-state values at long interaction distance. This energy exchange phenomenon can be explained by considering established atomic coherences among various atomic states and quantum interferences between three-photon and five-photon excitation pathways. Understanding these highorder nonlinear optical processes and interplays between them can be very important for correlated FWM or SWM photon-pair generations and quantum information processing.