Polychromatic-field-induced transparency and absorption in a three-level Λ system

We report an experimental study of atomic coherence and interference in a three-level Lambda system of cold Rb atoms driven by multicolor coupling and probe fields. The multicolor coupling and probe fields open multiple channels for a two-photon Raman process. Interference between the open channels leads to rich spectral features in the Lambda system and can be controlled by the phase of the probe field. The constructive-interference-induced transparency or the destructive-interference-induced absorption with a subnatural linewidth can be selectively created near the atomic resonance.