Researchers from Southeast University in China have created a new artificial surface that can bend and focus electromagnetic waves similar to an antenna.
The achievement, which the team is calling “the first broadband transformation optics metasurface lens,” could lead to the creation of new types of antennas that are flat, ultra low-profile or that conform to the shape of curved surfaces.
Described in the journal Applied Physics Letters, the new metamaterial is comprised of a dielectric material coated with tiny, metallic U-shaped structures. It exhibits properties similar to those of a Luneburg lens, spherical optics that interact with light in a unique way, according to the researchers.
“In a Luneburg lens, the index of refraction varies across the spherical lens body, making it very different than a normal lens. Luneburg lenses can focus light or incoming electromagnetic waves to an off-axis point at the edge of the lens (not directly in front or behind it as a normal lens would do). Or they can uniformly channel electromagnetic waves emanating from a nearby point source and radiate them in a single direction — something no spherical lens can do.”
Luneburg lenses are often used as radar reflectors and microwave antennae, but are unsuitable for many other applications due to their spherical nature, Tie Jun Cui said. The development of a flat lens with the properties of a Luneburg lens could remove this issue and enable a wider variety of applications.
According to Cui, the new research compliments the traditional method of constructing Luneburg lenses based on geometric optics, as well as a second way discovered in the last few years that uses holographic optics.
“We now have three systematical designing methods to manipulate the surface waves with inhomogeneous metasurfaces, the geometric optics, holographic optics, and transformation optics,” he said. “These technologies can be combined to exploit more complicated applications.”