Negatively refracting atomic vapour

Abstract

A new mechanism for realizing negative refractive index with a four-level atomic system is suggested. The explicit expressions for the electric permittivity and magnetic permeability at probe frequency are presented. It is shown that there is a frequency band in which the four-level photonic-resonant atomic vapour may exhibit simultaneously negative permittivity and permeability, and that such an atomic vapour may become a left-handed material (negatively refracting medium). Compared with the previous schemes to realize negative refraction within the framework of classical electromagnetic theory, the most remarkable features of the present scenario are as follows: (i) isotropic material with microscopic structure units at atomic-scale level, (ii) negative refraction in visible and infrared frequency bands, (iii) controllable manipulation by external fields and (iv) based on quantum coherence in a multilevel atomic system.