Triplet-level-crossing emission resonances in backward degenerate four-wave mixing

P. Mathey, Grégory Gadret, Konstantin Shcherbin

E. Köster, J. Mlynek, Wulfhard K. Lange

M. Pinard, B. Kleinmann, G. Grynberg

C. Schmidt-Iglesias, R. Corbalán

Resonant backward degenerate four-wave mixing in a (Lambda) -type Doppler-broadened 3- level system using two arbitrarily intense copropagating and crosspolarized pump beams is analyzed. The saturation features of the emission spectra are shown to depend critically on the pump imbalance and in case of a balanced grating wave saturation level-crossing emission resonances arising from destructive interference effects between coherent excitation pathways are shown to appear.

Karsten K. Rottwitt

M. Pinard, Philippe Verkerk, G. Grynberg

The effect of an intense pump beam on the intensity of the phase-conjugated emission is studied in the case of a three-level atom. We first extend to the case of cross-polarized pump beams the dressed-atom model that we have presented previously [Phys. Rev. A 34, 4008 (1986)] for the case of two-level atoms. The range of validity of our theory is \ensuremath{\Gamma} (natural width) ${\ensuremath{\Omega}}_{1}$ (Rabi frequency of the intense pump) ku (Doppler width). We have studied the line shape in degenerate four-wave mixing, the influence of a static magnetic field, and the resonances that appear in nondegenerate four-wave mixing. Experiments are done in a neon discharge using cw dye lasers. The experimental results are in good agreement with the theoretical predictions. In degenerate four-wave mixing, we have shown that the saturating dip disappears when the weak beams have orthogonal polarizations. In the presence of a static magnetic field and in the nearly degenerate case, narrow resonances corresponding to transitions between energy levels of the dressed atom are observed. The intensity and the width of these resonances are in very good agreement with the predictions of the theoretical model.