Tunable electromagnetic 'invisible gateway' brings science closer to fiction
August 26, 2009
Harnessing the unique properties of metamaterials, researchers in China have recently published a work detailing the implementation of a thin air, broadband and remotely controllable 'invisible gateway' that is able to shield all types of electromagnetic waves while letting through all other physical objects.
In the paper published by the group from the Hong Kong University of Science and Technology and the Fudan University in Shanghai, this newly-developed technology is compared to one of the 'hidden portals' often mentioned in fiction that is now coming much closer to reality.
In its study, the group made use of negative refractive index metamaterials, exotic materials that can refract light and other electromagnetic waves in unique ways that are currently a very active field of research in solid state physics and electrical engineering.
The group employed metamaterials in conjunction with ferrite materials and transformation optics to produce a complex scattering effect that bends light and other electromagnetic waves away from the gateway, preventing them from walking through. However, because of the shape of the device (pictured above), other objects easily can go through the portal undisturbed, as nothing but thin air separates the two sides of the gateway.
Unlike previous attempts at building such a gateway, the team's approach seems to have solved the problem of the narrow operational bandwidth that is typical of metamaterials, which means that only a very narrow range of frequencies would be effectively blocked out on command.
This configuration, in fact, can be manipulated to have optimum permittivity and permeability, and is able to insulate the electromagnetic field that encounters it with an appropriate magnetic reaction. What is more, the configuration's response to magnetic fields can even be tuned and switched on and off remotely.
Does this mean that the long sought-after invisibility cloak will soon see the light of day? Not yet, according to Dr Huanyang Chen, who was part of the research group: "In the frequency range in which the metamaterial possesses a negative refraction index, people standing outside the gateway would see something like a mirror. Whether it can block all visible light depends on whether one can make a metamaterial that has a negative refractive index from 300 to 800 nanometers [the visible spectrum]," he explained.
As of today, such a composite hasn't been created. However, the team's findings have revealed yet another possible path to a Harry Potter-style invisibility cloak.
Paper: A simple route to a tunable electromagnetic gateway, Huanyang Chen, Che Ting Chan, Shiyang Liu, Zhifang Lin
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