Low-loss negative refraction by laser induced magneto-electric cross-coupling

TL;DR

This paper proposes a method to achieve negative refraction with low absorption using laser-induced magneto-electric cross-coupling in atomic media, enabling better control and reduced losses in negative index materials.

Contribution

It introduces a novel scheme for negative refraction via coherent electric-magnetic dipole coupling, reducing required dipole density and absorption, with tunable refractive index and impedance matching.

Findings

Negative refraction achieved at lower dipole densities.

Absorption minimized through destructive quantum interference.

Impedance matching to vacuum is feasible.

Abstract

We discuss the feasibility of negative refraction with reduced absorption in coherently driven atomic media. Coherent coupling of an electric and a magnetic dipole transition by laser fields induces magneto-electric cross-coupling and negative refraction at dipole densities which are considerably smaller than necessary to achieve a negative permeability. At the same time the absorption gets minimized due to destructive quantum interference and the ratio of negative refraction index to absorption becomes orders of magnitude larger than in systems without coherent cross-coupling. The proposed scheme allows for a fine-tuning of the refractive index. We derive a generalized expression for the impedance of a medium with magneto-electric cross coupling and show that impedance matching to vacuum can easily be achieved. Finally we discuss the tensorial properties of the medium response and derive expressions for the dependence of the refractive index on the propagation direction.