An Invisible Metallic Mesh

TL;DR

This paper presents a novel metallic mesh that is effectively invisible at certain frequencies, achieved by aligning scattering resonances, enabling applications like perfect antenna radomes without disturbing electromagnetic fields.

Contribution

The authors analytically, numerically, and experimentally demonstrate that corrugated metallic wires can be designed to have near-zero scattering by aligning multiple scattering channels, creating a self-invisible material.

Findings

Record-low scattering amplitudes achieved

Effective parameters nearly identical to air

Indistinguishable transmission spectra across arrangements

Abstract

We introduce a solid material that is itself invisible, possessing identical electromagnetic properties as air (i.e. not a cloak) at a desired frequency. Such a material could provide improved mechanical stability, electrical conduction and heat dissipation to a system, without disturbing incident electromagnetic radiation. One immediate application would be towards perfect antenna radomes. Unlike cloaks, such a transparent and self-invisible material has yet to be demonstrated. Previous research has shown that a single sphere or cylinder coated with plasmonic or dielectric layers can have a dark-state with considerably suppressed scattering cross-section, due to the destructive interference between two resonances in one of its scattering channels. Nevertheless, a massive collection of these objects will have an accumulated and detectable disturbance to the original field distribution. Here we overcome this bottleneck by lining up the dark-state frequencies in different channels. Specifically, we derive analytically, verify numerically and demonstrate experimentally that deliberately designed corrugated metallic wires can have record-low scattering amplitudes, achieved by aligning the nodal frequencies of the first two scattering channels. This enables an arbitrary assembly of these wires to be omnidirectionally invisible and the effective constitutive parameters nearly identical to air. Measured transmission spectra at microwave frequencies reveal indistinguishable results for all the arrangements of the 3D-printed samples studied.