Velocity-selective effect and its use in refractive index control by an incoherent pumping in a V-type electromagnetically-induced-transparency medium

Refractive index control and its relevance to the velocity-selective effect generated by the propagation direction of the incoherent pumping field are studied in an open V-type atomic system. The velocity-selective effect on electromagnetically-induced transparency (EIT) is presented in theory and verified in the experiment. It shows that, in contrast to the case of copropagation, counter-propagation of the incoherent pumping field has an absolutely opposite effect on the dispersion of the V-type EIT system. The experimental results are in good agreement with the theoretical analysis.