Science fiction might soon evolve into science fact
URBANA – Harry Potter's invisibility cloak may soon be within the reach of any ordinary American with a little silicon photonic crystal and a Ph.D. in engineering.
Say you have a battleship and you want to park it in the Boneyard without plugging quarters into Champaign's exorbitant meters. The cloak thought up by two University of Illinois researchers would bend light around the battleship, saving you from getting a ticket.
The mathematical concept created by postdoctoral research associate Dong Xiao won't be ready any time soon for purchase at Target. He and co-researcher Harley Johnson, a Cannon Faculty Scholar and professor of mechanical science and engineering, just published their concept in a scientific journal, Optics Letters, but they don't have a working model.
The idea, Xiao says, is that concentric rings of silicon photonic crystals can be tailored to specific light wavelengths, allowing light to flow around the object, like "water flowing around a rock."
Ideally, Johnson said, the object would be spherical, appearing identical from any direction. But for a battleship on the water, he said, a ring would be sufficient to hide it from sea-level observers.
"The spacing is the key," Xiao says.
The idea sounds like science fiction – and in fact was science fiction, in H.G. Wells' "The Invisible Man" – but there's been a lot of activity in the realm of real science in the last few years, leading the pair to have an huge enthusiasm for the subject, tempered by a good sense of humor.
In 2006, a team of scientists at Duke University's Pratt School of Engineering showed off an "invisibility cloak" that deflects microwave beams so they flow around a object. They used artificial "metamaterials" arranged in a series of concentric circles to deflect microwaves.
The UI advance is possibly more useful and certainly way cooler in that it would work with many wavelengths, including visible light, not just microwaves. In fact, Xiao says, the discovery applies to any type of electromagnetic wave, including infrared.
It's also a departure from what mechanical engineers generally do, Johnson points out. Such work is usually the province of physicists or materials scientists.
However, the researchers are not ready to suggest they have created total invisibility. Because there can be distortion, they term it "approximate cloaking."
While the idea, when it reaches its full potential, will obviously have applications in lucrative fields like defense technology and other areas not yet dreamed of, it's unlikely that you'll ever see – or not see – humans walking around in spheres of invisibility.
"I don't expect to make myself invisible," Johnson says.