Zero absorption and large negative refractive index in a left-handed four-level atomic media

In this paper,we have investigated three external fields interacting with the four-level atomic system described by the density-matrix approach.The atomic system exhibits left-handedness with zero absorption as well as large negative refractive index.Varying the parameters of the three external fields,the properties of zero absorption,large negative refractive index from the atomic system keep unvarying.Our scheme proposes an approach to obtain negative refractive medium with zero absorption. The zero absorption property of atomic system may be used to amplify the evanescent waves that have been lost in the imaging by traditional lenses.And a slab fabricated by the left-handed atomic system may be an ideal candidate for designing perfect lenses.