Metamaterials Enhanced to Improve Invisibility Functions

Nathan Landy with invisibility device (Duke University)

Researchers at Duke University in North Carolina improved the invisibility functions of materials engineered to deflect light waves and hide objects from view, with potential uses in fiber optic communications. Engineering graduate student Nathan Landy and professor David Smith published their findings online yesterday in the journal Nature Materials (paid subscription required).

In 2006, Smith and colleagues from Duke and Imperial College London devised an invisibility cloak with materials engineered to interact with electromagnetic waves that limit their visual properties. These engineered materials, called metamaterials, can limit both reflections and shadows to make them undetectable. Objects made with these metamaterials can guide electromagnetic waves around an object, and have them emerge at a further point as if they had passed through empty space

Landy (pictured left) and Smith improved on the original work by filling in and adjusting some of the original assumptions about invisibility. “In order to create the first cloaks, many approximations had to be made in order to fabricate the intricate metamaterials used in the device,” says Landy. One of those issues, Landy notes, is the “loss of the waves due to reflections at the boundaries of the device,” which he describes as analogous to light reflecting off glass.

The original invisibility cloak device had parallel and intersecting strips of fiberglass etched with copper, and divided into four quadrants. “Each quadrant of the cloak,” says Landy, “tended to have voids, or blind spots, at their intersections and corners with each other.” The improved device takes the same basic design and adds copper strips to create a more complex material, but one that removes the reflections at the margins.

“It split light into two waves which traveled around an object in the center,” adds Landy, “and re-emerged as the single wave with minimal loss due to reflections.” This property of the metamaterials, the researchers suggest, could be applied to fiber optic communications, that can help make straighten the light paths carrying large volumes of data and reduce attentuation of the waves when they bend.

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