Refraction of Electromagnetic Energy for Wave Packets Incident on a Negative Index Medium is Always Negative

TL;DR

This paper proves that electromagnetic wave packets always refract negatively when passing from positive to negative index media, with both energy and group refraction consistently negative, clarifying a fundamental aspect of negative index materials.

Contribution

It provides a definitive proof that energy and group refraction are always negative in negative index media, resolving previous ambiguities.

Findings

Energy is always negatively refracted.

Group refraction of wave packets is always negative.

Clarifies fundamental behavior of electromagnetic waves in negative index media.

Abstract

We analyze refraction of electromagnetic wave packets on passing from an isotropic positive to an isotropic negative refractive index medium. We definitively show that in all cases the energy is always refracted negatively. For localized wave packets, the group refraction is also always negative.