meta-material, Metal-free

Scientists at the Duke University have developed the first metal-free, dynamically tunable metamaterial for regulating electromagnetic waves, i.e. it can be tuned by light. The strategy could form the foundation for technologies varying from advanced security scanners to new types of visual displays.

The outcomes appeared on April 9 in the journal Advanced Materials. A metamaterial is a man-made material that manipulates waves like light and sound by properties of its construction rather than its chemical buildup. Scientists can create these materials to have rare or abnormal properties, like the capability to absorb particular 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,” said Willie Padilla, a professor of electrical and computer engineering at Duke. “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.”

In the new technology, each grid position carries a little silicon cylinder just 50 microns high and 120 microns broad, with the cylinders aligned 170 microns apart from one another. While silicon is not commonly a conductive material, the researchers bombard the cylinders with a particular frequency of light in a method called photodoping. This imbues the typically insulating material with metallic features by stimulating electrons on the cylinders’ surfaces.

These recently relieved electrons make the cylinders to associate with electromagnetic waves moving through them. The size of the cylinders directs what frequencies of light they can communicate with, while the angle of the photodoping affects how they shape the electromagnetic waves. By purposefully superintending these features, the metamaterial can regulate electromagnetic waves in many different styles.

For this research, the cylinders were sized to associate with terahertz waves—a band of the electromagnetic spectrum that lies between microwaves and infrared light. Regulating this wavelength of light could enhance broadband interactions between satellites or lead to security technology that can effortlessly scan through clothing. The strategy could also be adapted to other bands of the electromagnetic spectrum—like infrared or visible light—simply by scaling the capacity of the cylinders.

“We’re illustrating a new field where we can dynamically command each point of the metasurface by regulating how they are being photodoped,” Padilla said. “We can generate any type of design we want to, enabling us to form lenses or beam-steering devices, for instance. And because they’re regulated by light beams, they can change very fast with very small power.”

While existing metamaterial takes control of the electromagnetic waves through their electric characteristics, the new technology can additionally manipulate them through their magnetic characteristics.

“This enables each cylinder to not only direct the incoming wave but the interaction between adjacent cylinders,” said Kebin Fan, a research scientist in Padilla’s laboratory and first writer of the paper. “This provides the metamaterial much more versatility, such as the capability to control waves moving across the surface of the metamaterial rather than within it.”

“We’re more excited in the basic illustration of the physics behind this technology, but it does have a few remarkable features that make it engaging for devices,” Padilla said.

“Because it is not formed of metal, it won’t melt, which can be an obstacle for some purposes,” he said. “It has subwavelength control, which provides you more freedom and versatility. It is also plausible to reconfigure how the metamaterial affects incoming waves very quickly, which has our group mapping to investigate using it for dynamic holography.”

Research Scientists at the Duke University developed the first metal-free, dynamically tunable metamaterial for as to managing electromagnetic waves, i.e. it can easily be tuned by light. The approach could make the basis for technologies varying from advanced security scanners to new types of visual displays. A metamaterial is an artificial material, and this time a dynamically tunable, that regulates waves like light and sound by properties of its construction rather than its chemistry.


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