Electric and magnetic dipole allowed transitions of atoms for three-dimensionally isotropic left handedness in a mixed atomic vapor

Since previous negative-index atomic media based on quantum optical approaches are highly lossy, a proposal for realizing a three-dimensionally isotropic left-handed atomic vapor medium is suggested based on a mechanism of incoherent gain assisted atomic transitions. Two three-level atomic systems are utilized for producing simultaneously negative permittivity and negative permeability, respectively, in the same frequency band. We suggest that fine and hyperfine level transitions of atoms (e.g., a hyperfine level transition in a hydrogen atomic system and a fine level transition in an alkali-metal atomic system) would be applicable to realization of such a negatively refracting atomic vapor. The attractive features of the present scenario include: i) three-dimensionally isotropic negative indices; ii) incoherent gain wave amplification in the negative-index atomic vapor; iii) tunable negative indices depending upon external fields. Such a left-handed quantum optical medium can serve as a supporting substrate for lossy negative-index materials for loss compensation. It can also be used in designing new quantum optical and photonic devices (e.g., a subwavelength focusing system and a negative-index superlens for perfect imaging) because of its attractive properties of three-dimensional isotropy and high-gain wave amplification.
QC 20140613