Control of light in an M-type five-level atomic system

An M-type five-level atomic model is proposed to achieve a large index of refraction with vanishing absorption. We present a novel model, to our knowledge, in theoretical analysis, in which an incoherent pumping rate is adopted to simplify the M-type five-level system to be an equivalent four-level system. The theoretical and experimental results show that, by adjustment of the intensity of the incoherent pump, lower group velocity (than that obtained in a conventional A-type three-level electromagnetically induced transparency system) is obtained in cesium atomic vapor. Moreover, a saturation limit for the group velocity is also presented. The experimental results show good agreement with the theoretical analysis. (C) 2005 Optical Society of America.