This work was supported by the National ScienceFoundation of China for Distinguished Young Schol-ars (No. 60325414), the Natural Science Foundation ofShanxi Province (No. 20031007), and Shanxi ReturnedScholar Funds
We report an experimental observation of the variation in linewidth of the electromagnetically induced transparency (EIT) resonance in a three-level A-type system for several laser bandwidths in a Rb vapor cell, wit...