Imagine planes invisible -- literally -- to radar; a sub slipping beneath the waves hidden completely from any attempt at a sonar ping; a tank impervious to infrared sensors.
With planes it's geometry and materials. With subs its materials, tactics and sound alleviators. With tanks -- well, we haven't gotten there yet. But scientists have successfully tested active cloaking from certain types of radiation, including microwaves.
"It's a brand new method of cloaking," Milton adds. "It is two-dimensional, but we believe it can be extended easily to three dimensions, meaning real objects could be cloaked. It's called active cloaking, which means it uses devices that actively generate electromagnetic fields rather than being composed of 'metamaterials' [exotic metallic substances] that passively shield objects from passing electromagnetic waves."
Milton says his previous research involved "just cloaking clusters of small particles, but now we are able to cloak larger objects."
For example, radar microwaves have wavelengths of about four inches, so Milton says the study shows it is possible to use the method to cloak from radar something 10 times wider, or 40 inches. That raises hope for cloaking larger objects. So far, the largest object cloaked from microwaves in actual experiments was an inch-wide copper cylinder.
According to the report, this method could be more effective across a wider range of bandwidths. In other words, one active cloaking module could render the object invisible to many sources of emissions. Previous iterations involved materials that cloak against a single bandwidth or wavelength.
"The problem with metamaterials is that their behavior depends strongly on the frequency you are trying to cloak from," he adds. "So it is difficult to obtain broadband cloaking. Maybe you'd be invisible to red light, but people would see you in blue light."
Most previous research used interior cloaking, where the cloaking device envelops the cloaked object. Milton says the new method "is the first active, exterior cloaking" technique: cloaking devices emit signals and sit outside the cloaked object.
Be sure to read the scientists' article in Optics Express journal HERE and watch the demonstration video. Can it cloak me from my boss, I wonder?