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New Way to Produce Negative Refraction Achieved

Category: Science & Technology
Posted: 11:18AM
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It took some time for scientists to accept that light is an electromagnetic phenomenon, but now we know that because it must obey mathematical laws we can make it do unnatural things. Metamaterials are any man-made material that exhibit properties impossible to find in nature, but are normally associated with light as researchers use them to create invisibility cloaks. Now researchers at Harvard University's School of Engineering and Applied Sciences have found a new way to create a metamaterial that has quite extreme properties.

Key to the creation of invisibility cloaks is making materials with a negative index of refraction. This means that when light enters the material it bends in the opposite direction one would expect from natural materials. Normally this is achieved in metamaterials via magnetic inductance but the Harvard researchers decided to try using kinetic inductance. The result is a metamaterial with a refractive index of -700 (water's is 1.333) and the ability to squeeze light to ultra-subwavelength sizes. Normally there is a diffraction limit that prevents light from being squeezed to smaller than half its wavelength.

The researchers did this proof-of-concept work with microwaves at 20 K, but believe it can be replicated with terahertz waves at room temperature. Graphene will also be needed at the high temperature as a 2D conductor, instead of a 2D electron gas the microwave design was using. Room temperature operation combined with the ultra-subwavelength scale of the light could allow for advance photonics to be integrated into chips.



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