Mathematicians at the University of Utah (Salt Lake City, UT) have theoretically demonstrated a new broadband exterior cloaking technique that uses active wave-emitting devices to cancel incoming radiation, rendering an object inside the cloaked region invisible. The use of active devices for cloaking has two main advantages: it is relatively easy to design cloaking devices that work over a broad range of frequencies and the devices do not need to completely surround the object. The principle behind the devices is the same as in noise-canceling headphones; therefore, one needs to know the form of the incoming pulse in advance.
For cloaking in a regime corresponding to s-polarized microwaves in air with a 12.5 cm central wavelength and 2.4 GHz bandwidth, an object as large as 1.25 m in radius could be cloaked. A possible application for this method is to render a submarine invisible from sonar, or—on the borderline of what is possible—divert a tsunami from an oil rig. Contact Fernando Guevara Vasquez at [email protected].