Doppler-broadened four-wave mixing under double-resonance optical pumping in the 5S1/2-5P3/2-4D5/2 transition of warm 87Rb atoms

We investigate stimulated four-wave mixing (FWM) in the 5S(1/2)-5P(3/2)-4D(5/2) transition of warm Rb-87 atoms. Here, the telecommunication wavelength (1529 nm) of the 5P(3/2)-4D(5/2) transition is nearly twice that of the 5S(1/2)-5P(3/2) transition (780 nm). The observed FWM signals of the 5P(3/2)-4D(5/2) transition indicate that the FWM process is significantly influenced by the two-photon Doppler broadening due to the wavelength difference between both transitions and the double-resonance optical pumping (DROP) effect due to two-step excitation. We elucidate the suppression of the FWM process due to the DROP effect using a simple six-level atomic model. (C) 2021 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement