We propose two dense gas schemes of four-level 'Lambda'-type and V-type atoms based on the effect of quantum coherence. It is shown that under certain conditions the dense gas can simultaneously exhibit negative permittivity and negative permeability, and thus become a negative refractive-index material. Furthermore, by analyzing the absorption property of the left-handed materials, we find that the absoption can be reduced via choosing appropriate parameters. Such schemes might be used to fabricate isotropic and homogeneous left-handed material with vanishing absorption in a wider optical frequency band.
© 2007 Chinese Optics LettersPDF Article