The ultrathin cloak creates an effect that makes it seem like the light were hitting a perfect mirror and the cloak and object weren't even there. Even the edges are invisible with the new device, the researchers said.
With the proper tuning of the gold bricks, it's not hard to make the reflected light look like anything you want - either the background of the object (a floor, for example) or something else entirely, Zhang told Live Science. If the cloak were big enough, theoretically, you could drape it over anything. "You could cover a tank with it and make it look like a bicycle," he added.
Although the cloak Zhang and his colleagues made is tuned to hide objects from light reflected at a wavelength of 730 nanometers, there's no reason it can't work with multiple wavelengths, Zhang said. [Science Fact or Fiction? The Plausibility of 10 Sci-Fi Concepts]
The reflection trick also works from any angle, and the cloak doesn't have to be a certain shape - it can be wrapped around anything, and the effect still works. It's also thin and light, according to the researchers.
But there is one disadvantage: If Harry Potter were wearing this cloak, he'd have to stay still for it to work, since the tuning has to be matched to the background.
Andrea Alù, an associate professor of electrical engineering at the University of Texas at Austin, has done extensive research on cloaking systems. He is skeptical that scientists can create the kind of illusion Zhang describes.
"They had a small object, a little bump," Alù told Live Science. "With a larger object, I can't take advantage of that ... when I illuminate it, a portion is not illuminated; it's in shadow." As such, the illusion of the perfect reflector would be broken, he said.
Even so, the new findings show you can manipulate how light reflects using nanometer-scale structures on a thin surface. "The beauty of the paper is that you can control the reflection surface at the sub-wavelength scale," Alù said.
Zhang said the cloaking technology's reflectivity offers another application: displays. Right now, any big projection (e.g., a movie in a theater) has to use a relatively flat surface. But if the phase and frequency of the light reflected from it could be finely controlled, that problem could go away. A projection surface could be any shape, and the resulting picture would not be distorted.
Zhang added that this kind of material has been fabricated before, and that a next step would be to make a lot of it at industrial scales, tuning the antennas to different wavelengths of light.
The new study was published online in the journal Science.
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