Dressed Four-Wave Mixing From Upper Branch in a Sodium Atomic Vapor

With electromagnetically induced transparency-assisted configuration, a four-wave mixing (FWM) process generated from the upper branch of a cascade-type three-level atomic system is studied both theoretically and experimentally. Through the advantage of neglecting the absorption of a FWM signal due to a much smaller transition probability of a two-photon process, we easily observe the Autler-Townes effect altering the energy levels in such FWM processes. Meanwhile, the multiplied line shapes of a FWM spectrum are investigated by varying the frequency detuning. By applying external field, such FWM processes can be manipulated through modulating the dark state. Finally, conversion efficiency is considered by changing the temperature of oven, which shows a threshold temperature point. Theoretical interpretations correspond well with the experimental data.