Effect of injected noise on electromagnetically induced transparency and slow light

Abstract

We have examined theoretically the phenomenon of electromagnetically induced transparency (EIT) in a three-level system operating in the Λ-configuration in the presence of an externally injected noise coupling the ground level to the intermediate (metastable) level. The changes in the depth and width of the induced transparency and the slowing down of the probe light have been calculated as a function of the probe detuning and strength of the injected noise. The calculations are within the rotating-wave approximation. Our main results are the reduction and broadening of the EIT with increasing strength of the injected noise, and a reduction in the slowing down of group velocity of the probe-laser beam. Thus, the injected semi-classical noise, unlike the quantum dynamical noise associated with the spontaneous emission, is not effectively cancelled by the EIT mechanism.