Gradient index metamaterials

TLDR

Metamaterials are artificially structured materials with tailored electromagnetic responses that can achieve properties difficult to realize with conventional materials, and the proposed gradient‑index material may be suited for terahertz applications where split‑ring resonators exhibit magnetic resonance. The study presents a structured metamaterial based on conducting split‑ring resonators that achieves a constant spatial gradient in its effective index of refraction. The authors fabricated a planar slab of the SRR‑based metamaterial and experimentally confirmed its gradient index by measuring microwave beam deflection across a broad frequency range. The gradient‑index metamaterial, confirmed by microwave beam deflection experiments, offers an alternative to conventional gradient‑index lenses and may be advantageous at higher frequencies, including terahertz applications where SRRs exhibit magnetic resonance.

Abstract

Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult to achieve with existing materials. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index-of-refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a broad range of frequencies. The gradient index metamaterial represents an alternative approach to the development of gradient index lenses and similar optics that may be advantageous, especially at higher frequencies. In particular, the gradient index material we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated.