A team of researchers from Duke University developed the first metal-free metamaterial for regulating electromagnetic waves.
This metal-free metamaterial can be dynamically tuned to regulate electromagnetic waves. The researchers believe that their discovery could form the foundation for technologies such as advanced security scanners and different types of visual displays.
The scientist’s findings were published in the journal Advanced Materials.
A metamaterial is an artificial material that can control waves like sound and light by its construction properties rather than its chemical buildup.
Scientists create these materials to produce rare or abnormal features like the capability to absorb specific ranges of the electromagnetic spectrum or to turn light backward.
“These materials are built of a network of separate units that can be independently tuned,” Willie Padilla, a professor of electrical and computer engineering at Duke University, said.
“As a wave moves through the surface, the metamaterial can regulate the amplitude and phase at every location in the network, which allows us to manipulate the wave in a lot of various ways.”
The new metamaterial is said to carry a little silicon cylinder that is 50 microns high and 120 microns broad. The cylinders are then aligned 170 microns apart from one another.
Since silicon is not usually a conductive material, the researchers hit the cylinders with a specific light frequency in a technique known as photodoping. This technique imbues the insulating material with metallic features through the stimulation of electrons on the surface of the cylinder.
The excited electrons allow the cylinders to interact with the electromagnetic waves coursing through them. The frequencies of light the cylinders interact with is based on the size of these waves. On the other hand, the photodoping angle affects how the cylinders manipulate the electromagnetic waves.
“We’re demonstrating a new field where we can dynamically control each point of the metasurface by adjusting how they are being photodoped,” Padilla further explained.
“We can create any type of pattern we want to, allowing us to create lenses or beam-steering devices, for example. And because they’re controlled by light beams, they can change very fast with very little power.”
To date, existing metamaterials have controllled electromagnetic waves through their electric properties. However, the new technology developed by the Duke researchers could manipulate them through their magnetic properties.
“This allows each cylinder to not only influence the incoming wave, but the interaction between neighboring cylinders,” Kebin Fan, a research scientist in Padilla’s laboratory and first author of the paper, said.
“This gives the metamaterial much more versatility, such as the ability to control waves traveling across the surface of the metamaterial rather than through it.”
According to Padilla, they are more interested “in the basic demonstration of the physics” behind their new technology.
“Because it is not made of metal, it won’t melt, which can be a problem for some applications. It has subwavelength control, which gives you more freedom and versatility. It is also possible to reconfigure how the metamaterial affects incoming waves extremely quickly, which has our group planning to explore using it for dynamic holography,” Padilla went on to say.