Wedge - Shaped Absorbing Samples Look Left Handed: The Problem of Interpreting Negative Refraction, and its Solution

TL;DR

This paper demonstrates that wedge-shaped absorbing samples can mimic negative refraction phenomena, highlighting the importance of careful interpretation in experiments involving left-handed materials and proposing a definitive test with metamaterials.

Contribution

The study reveals that observed negative refraction in wedge-shaped samples can result from wave losses rather than true negative index, and proposes an experiment to conclusively determine the nature of refraction.

Findings

Wedge-shaped absorbing samples can mimic negative refraction.

Wave losses dominate over propagation in certain conditions.

Proposed experiment with metamaterials to determine true refraction sign.

Abstract

We report experiments of light transmissivity at wavelengths: 532 and 400 nm, through an Au film with a wedge shape. Our results mimic the negative refraction reported by others for so-called left handed materials. A mimic of negative refraction is observed, even though this medium is well known to be right handed, and thus its refractive index has a positive real part. Analogous results are obtained with a glass wedge at 320nm where absorption dominates. The experiment is explained by the wave losses that dominate over propagation, like in the observation of negative refraction, already reported in developed metamaterial wedges. We design and propose an experiment with metamaterials by using thicker wires, in correspondence with light experiments that should conclusively determine whether refraction is positive or negative.