UI researchers to develop an invisibility cloak

By Peter Kim

Nothing is worse than getting to the baseball stadium only to find your view blocked by an obnoxious metal pillar. University researchers say in the future you may be able to solve your problem by simply making it disappear.

University Professor Harley Johnson and researcher Dong Xiao have developed the scientific blueprint for the first invisibility cloaking device.

“Optical cloaking is clearly an exciting breakthrough in the last two years in the scientific and engineering society,” said Nicholas Fang, nanophotonics researcher at the University. “The general concept of cloaking was proposed about three years ago, but until last year it was purely a mathematical beauty on paper.”

While a prototype has yet to be built, Johnson foresees many possibilities with invisibility cloaking devices ranging from military security to baseball stadiums to sound-proof houses.

“The first people working on it would be the military or defense industry,” Johnson said. “They could use it to conceal devices used for surveillance.”

Get The Daily Illini in your inbox!

  • Catch the latest on University of Illinois news, sports, and more. Delivered every weekday.
  • Stay up to date on all things Illini sports. Delivered every Monday.
Thank you for subscribing!

The cloaking device’s key element is silicon, a common material that is present in everything from computer chips to breast implants.

The cloaking device would be more of a container than a garment-like cloak. By connecting thin concentric rings of silicon, a circular container is formed, Johnson said. The silicon rings form a barrier that acts like a Teflon coating for light waves.

“When we see things, light bounces off an object and goes into our eyes,” Johnson said. “With the cloaking device, light bends around the object and then goes to your eyes. You can’t see the container or anything inside it. You see what’s behind it.”

The cloaking device developed by Johnson and Xiao is two-dimensional and flat. However, their design can be extrapolated from two dimensions to three. Instead of being a ring-shaped container with silicon circles, it would be ball-shaped with outer silicon shells.

While the object would be clearly invisible there could be some mirage-like waviness, Johnson added.

The applications, however, are not limited to visible light. The basic science of the cloaking device also works for sound. This time the container would be deflecting sound waves instead of light waves.

This would be useful for a number of things.

Take for example, a concert hall with a pillar that is undesirably deflecting sound and creating dead spots in the room. The cloaking device could cover up the pillar so that the sound waves could travel around it as if it wasn’t even there, Johnson said.

The cloaking device could also be used for sound-proofing. If a house is next to a busy street or a lot of noisy neighbors, the homeowner could encapsulate the house in a cloaking container to force all of the noise to flow around the house and not into it.

“Optical cloaking is still in its infancy, and in my view there are still many steps before some real cool applications like what we see in Harry Potter can be demonstrated,” Fang said. “However, I am optimistic that the study of this unique device and related phenomena could lead to (many applications).”