A team of electrical engineers at the Duke University Pratt School of Engineering created the first dielectric electromagnetic metamaterial, a synthetic material engineered to produce properties not found in nature, which can absorb electromagnetic energy without heating up.
A closer look at one of the cylinders comprising a new non-metal metamaterial. The arrows depict how different
aspects of an electromagnetic field interact with the cylinder. (Duke University)
The surface of the metamaterial, according to a report on the Duke website, is dimpled with cylinders (“like the face a Lego brick”) in order to absorb terahertz waves, although the engineers believe that this technique could be used to absorb any frequency.
The metamaterial was created with boron-doped silicon and through computer simulations the engineers were able to determine how terahertz waves would interact with differently sized cylinders. After finding the optimal size, they built the metamaterial with hundreds of cylinders arranged in rows. It absorbed 97.65 percent of the waves at 1.011 terahertz.
This could be a breakthrough for thermal imaging equipment, which has previously included metal components and heat up quickly. The process for isolating the metal, as the article noted, is both difficult and costly. This technology could also lead to more efficient lighting with incandescent bulbs needing to operate at temperatures well past the melting point of most metals.
The work was supported by the U.S. Department of Energy and the research was recently published in Optics Express.
According to the abstract:
“Metamaterial absorbers consisting of metal, metal-dielectric, or dielectric materials have been realized across much of the electromagnetic spectrum and have demonstrated novel properties and applications. However, most absorbers utilize metals and thus are limited in applicability due to their low melting point, high Ohmic loss and high thermal conductivity.
“Other approaches rely on large dielectric structures and / or a supporting dielectric substrate as a loss mechanism, thereby realizing large absorption volumes. Here we present a terahertz (THz) all dielectric metasurface absorber based on hybrid dielectric waveguide resonances.
“We tune the metasurface geometry in order to overlap electric and magnetic dipole resonances at the same frequency, thus achieving an experimental absorption of 97.5%. A simulated dielectric metasurface achieves a total absorption coefficient enhancement factor of FT=140, with a small absorption volume.
“Our experimental results are well described by theory and simulations and not limited to the THz range, but may be extended to microwave, infrared and optical frequencies. The concept of an all-dielectric metasurface absorber offers a new route for control of the emission and absorption of electromagnetic radiation from surfaces with potential applications in energy harvesting, imaging, and sensing.”