Evolution of four-wave mixing by controlling Raman coherence in a multi-dressed atomic system

Abstract

The evolution of enhanced four-wave mixing based on Raman coherence as the probe intensity increases is observed experimentally in an 85 R b atomic vapor system. We propose that for a Doppler-broadened Λ -type level system, the generated anti-Stokes field from one-photon resonance will be suppressed by the dressed-states resonance and can be controlled by the probe intensity, which influences the effective transverse relaxation rate of Raman coherence. When the probe field is not so weak, the double resonance for dressed states will greatly suppress the anti-Stokes emission at the central frequency, and the signal peak will be split. We show that this phenomenon is a result of the destructive polarization interference between atoms with different velocities from the two types of resonance. Based on our model, we present a new, to the best of our knowledge, interpretation of four-wave mixing enhancement in the conventional Λ -type electromagnetically induced transparency system.