Why is the refractive index cannot be negative

TL;DR

This paper discusses the fundamental reasons why the refractive index cannot be negative, especially in left-handed metamaterials and negative refraction media, emphasizing the conceptual and practical issues involved.

Contribution

It clarifies the theoretical limitations and misconceptions regarding negative refractive index in metamaterials and argues against considering it as a real, negative value.

Findings

Refractive index in negative refraction media cannot be unequivocally defined as negative.

The concept of a negative real refractive index is not practically expedient.

The paper highlights the conceptual issues with negative index media.

Abstract

It has been shown that for left-handed metamaterials and generally for negative refraction media the refraction index cannot be entered unequivocally and cannot be considered as real, and especially as negative. This index for above referred media is not expedient