Comment on "Total Negative Refraction in Real Crystals for Ballistic Electrons and Light" (Phys. Rev. Lett. 91, 157404 (2003))

TL;DR

This paper clarifies that amphoteric refraction observed at uniaxial crystal interfaces is a natural anisotropic effect, not indicative of negative refraction in left-handed materials, correcting a recent misinterpretation.

Contribution

It demonstrates that amphoteric refraction can occur within a single uniaxial crystal and is unrelated to negative refraction in left-handed materials.

Findings

Amphoteric refraction occurs in single uniaxial crystals.

Refraction phenomena are due to anisotropic media properties.

Negative refraction is not necessarily linked to amphoteric refraction.

Abstract

Recently, Zhang et al. (Phys. Rev. Lett. 91, 157404 (2003)) have demonstrated that an amphoteric refraction, i. e. both positive and negative refraction, may prevail at the interface of two uniaxial anisotropic crystals when their optical axes are in different directions. The authors subsequently made a correspondence between such a refraction with the negative refraction expected for Left Handed Materials (LHMs). Here we comment that the amphoteric refraction can be observed even with one uniaxial crystal, and the refraction is not related to the negative refraction expected for the much debated LHM. Rather, the phenomenon is a natural result of anisotropic media.