U mathematicians have developed a new cloaking method that one day might be able to render objects invisible to radar and sonar.
“Essentially, we have some devices that cancel incoming waves,” said Fernando Guevara Vasquez, an assistant U math professor. “This works the same as noise cancellation headphones, except we care about waves coming from the devices.”
Mathematicians have proven that it is possible for the cloaking devices to shield any shaped object within the electromagnetic field the device generates. This new device cancels incoming waves, making it possible to cloak from a broader band of wavelength, said Graeme Milton, senior author of the study and a U math professor.
Originally, Milton and his team of mathematicians had the idea to cloak a small cluster of objects. Later, Guevara Vasquez, Milton and Daniel Onofrei worked together to further explore this idea of cloaking and developed a similar theory that would work with even very low frequencies, Guevara Vasquez said.
Presently, the cloaked area is only two-dimensional. However, they expect that it will be possible to cloak three-dimensional objects. This means that planes could be shielded from radar and submarines invisible to sonar, Milton said. Using microwaves, the largest object they have been able to cloak is an inch-wide copper cylinder.
“The term invisibility has a broader meaning here,” Milton said. “It’s invisible to microwaves that don’t get any reflection. Invisibility to sonar means invisible to sound.”
The mathematicians have also suggested and proven mathematically that the technology could be used to shield buildings from earthquakes and coastal structures from tsunami waves.
But cloaking from visible light would be nearly impossible because the size of the waves are so small, Guevara Vasquez said. It would be difficult to build a sensor so small that only microscopic objects would be shielded, he said.
The only limitation these new devices seem to have is that they need to know everything about the incoming waves8212;when the pulse begins, the frequency and amplitude within that pulse8212;to be able to shield it, Milton said.
With the earthquakes, seismographs, which detect seismic waves generated by the earthquake, would have to send the necessary information to the devices, which would then send out a disruptive wave to shield the building. With light, the signal sent would have to be quicker than the speed of light.
“Light wave lengths are so small that it’s extremely hard to build a small enough antenna that would react quickly enough,” Guevara Vasquez said.
Other cloaking devices that use metamaterials (materials with exotic properties) have been developed but are not as effective, Guevara Vasquez said.
Since Milton and Guevara Vasquez are mathematicians, not researchers, the method has not been tested in the field. A study concerning the possibility of the new cloaking method was published Aug. 17 in Optics Journal and an online related article was released Aug. 14 in Physical Review Letters.