New metamaterial gives light a one-way ticket: ...The silver-glass structure is an example of a "hyperbolic" metamaterial, which treats light differently depending on which direction the waves are traveling...
While the second set of grates let light escape the material, their spacing was slightly different from that of the first grates. As a result, the reverse-direction grates bent incoming light either too much or not enough to propagate inside the silver-glass layers. Testing their structures, the researchers found that around 30 times more light passed through in the forward direction than in reverse, a contrast larger than any other achieved thus far with visible light.
Combining materials that could be made using existing methods was the key to achieving one-way transmission of visible light, Lezec says. Without the intervening silver-and-glass blocks, the grates would have needed to be fabricated and aligned more precisely than is possible with current techniques. "This three-step process actually relaxes the fabrication constraints," Lezec says.
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