New invisibility cloak technology can hide objects from radar

Canadian scientists say they've developed an effective invisibility cloak that can make different sizes and types of objects invisible to radar. Two researchers at the University of Toronto designed and tested a new approach to cloaking by surrounding an object with small antennas that collectively radiate an electromagnetic field, the university said in a release Tuesday. In a study published in the journal Physical Review X, Professor George Eleftheriades and doctoral student Michael Selvanayagam describe how the radiated field cancels out any waves scattering off the cloaked object. "We've taken an electrical engineering approach, but that's what we are excited about," Eleftheriades said. "It's very practical," When light hits any object and bounces back into a person's eyes, they see that object. When radio waves hit it, they bounce back to a radar detector, revealing the object. In the system devised by Eleftheriades and Selvanayagam, the object is wrapped in a layer of tiny antennas that radiate a field away from the object, canceling out any waves that would bounce back, making the object undetectable to radar. Although their cloaking system works with radio waves, the researchers said re-tuning it to work at other wave frequencies, including light, could use the same principle as the necessary antenna technology matures. "There are more applications for radio than for light," Eleftheriades said. "It's just a matter of technology -- you can use the same principle for light, and the corresponding antenna technology is a very hot area of research."