Light Fantastic: Flirting With Invisibility

“Increasingly, physicists are constructing materials that bend light the “wrong” way, an optical trick that could lead to sharper-than-ever lenses or maybe even make objects disappear.Last October, scientists at Duke demonstrated a working cloaking device, hiding whatever was placed inside, although it worked only for microwaves.

In the experiment, a beam of microwave light split in two as it flowed around a specially designed cylinder and then almost seamlessly merged back together on the other side. That meant that an object placed inside the cylinder was effectively invisible. No light waves bounced off the object, and someone looking at it would have seen only what was behind it.

The cloak was not perfect. An alien with microwave vision would not have seen the object, but might have noticed something odd. “You’d see a darkened spot,” said David R. Smith, a professor of electrical and computer engineering at Duke. “You’d see some distortion, and you’d see some shadowing, and you would see some reflection.”

A much greater limitation was that this particular cloak worked for just one particular “color,” or wavelength, of microwave light, limiting its usefulness as a hiding place. Making a cloak that works at the much shorter wavelengths of visible light or one that works over a wide range of colors is an even harder, perhaps impossible, task.

Nonetheless, the demonstration showed the newfound ability of scientists to manipulate light through structures they call “metamaterials.””

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