PORTLAND, Ore.Metamaterials absorbing incident microwaves, instead of diverting them around objects like an invisibility cloak, prompted Chinese researchers at Southeast University in Nanjing to claim they are created an "electromagnetic black hole."
The concentric circles of metamaterials that act as an almost perfect "black body"absorbing nearly all incident microwaves and converting it them to heathold the promise of enabling novel antennas, electromagnetic-wave harvesters and super-efficient thermal emitters, according to the researchers.
Like invisibility cloaks that divert electromagnetic waves around objects, the Chinese omnidirectional absorbing device uses alternating fields of dielectrics and resonatorshere I-shaped dielectric structures for its outer shell and Jerusalem-cross-shaped electric-field-coupled (ELC) resonators for its inner shell, respectively. About 60 concentric layers were constructed on a metamaterial disk measuring about 100 millimeters in diameter. As a result, all nearly all incident microwaves were absorbed and converted into heat.
|Omnidirectional electromagnetic absorber uses concentric "I-shaped" and "Jerusalem cross shaped" metamaterials (see legends) that act like artificial black hole for microwaves.|
The layered dielectric cylinders combine a lossy inner core and a lossless outer shell with radially varied permittivity, causing electromagnetic waves hitting the cylinder to bend spirally in the shell region, then get trapped and absorbed by the lossy core, with nearly zero loss from scattering according to the researchers, hence creating the perfect omnidirectional absorber.
Next the researchers plan to demonstrate that their technique can also be used a visible wavelengths by fabricating a nanoscale version of the device.