Chiral Negative-Index Metamaterials in Terahertz

TL;DR

This paper reports the first experimental demonstration of a chiral negative-index metamaterial operating at terahertz frequencies, which achieves negative refraction without requiring simultaneous negative permittivity and permeability, opening new avenues for terahertz device applications.

Contribution

It presents the first experimental realization of a chiral NIM with negative refractive index at terahertz frequencies using a single chiral resonance, simplifying the design compared to traditional NIMs.

Findings

Achieved negative refractive index down to n=-5 at terahertz frequencies.

Demonstrated negative refraction with only a single chiral resonance.

Showed that chirality lifts degeneracy for circular polarizations, enabling negative refraction.

Abstract

Negative index metamaterials (NIMs) give rise to unusual and intriguing properties and phenomena, which may lead to important applications such as superlens, subwavelength cavity and slow light devices. However, the negative refractive index in metamaterials normally requires a stringent condition of simultaneously negative permittivity and negative permeability. A new class of negative index metamaterials - chiral NIMs, have been recently proposed. In contrast to the conventional NIMs, chiral NIMs do not require the above condition, thus presenting a very robust route toward negative refraction. Here we present the first experimental demonstration of a chiral metamaterial exhibiting negative refractive index down to n=-5 at terahertz frequencies, with only a single chiral resonance. The strong chirality present in the structure lifts the degeneracy for the two circularly polarized waves and relieves the double negativity requirement. Chiral NIM are predicted to possess intriguing electromagnetic properties that go beyond the traditional NIMs, such as opposite signs of refractive indices for the two circular polarizations and negative reflection. The realization of terahertz chiral NIMs offers new opportunities for investigations of their novel electromagnetic properties, as well as important terahertz device applications.