Optical cages made of graphitic frameworks.

Abstract

In pursuit of perfect infrared (IR) radiation absorbers, we examined quasi-crystal structures made of graphite wires. Simulations on an array of subwavelength graphitic cages and cage-within-cage frameworks indicate a flat absorption coefficient between 10-30 µm. The concept could be scaled up through the 50-120 µm [far-IR, terahertz (THz)] region by a proper structural design. For cage-within-cage, the IR radiation energy is funneled toward the inner cage, resulting in a rather hot structure. At longer wavelengths (microwave region), the electrical conductivity dominates the negative dielectric effect, and experiments with copper cages indicate scattering resonances. Graphitic structures allude to some absorption even at microwave frequencies. Applications are envisioned as anti-fogging surfaces, adaptable electromagnetic shields, energy harvesting, and efficient absorbers in the far-IR (THz frequencies).