IT IS like a valve for light 鈥� the first material that transmits electromagnetic radiation in one direction only.
and colleagues at the Massachusetts Institute of Technology have made what鈥檚 known as a photonic crystal from an array of ferrite rods.
Ordinarily the rods reflect microwaves in all directions, but when Wang adds a strong magnetic field, everything changes. Microwaves bouncing off the magnetised rods in one direction are modified to become 鈥渆vanescent鈥�, fading as they travel. Waves heading the other way carry on unhindered.
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Wang is now working on plans to adapt his device for higher frequency radiation, moving into the terahertz and eventually the visible part of the spectrum. These photonic crystals may help create new components for optical communication and computing, including simple one-way routers analogous to electrical diodes, as well as wave-guides for light that are more efficient than optical fibres. 鈥淚t raises a lot of intriguing possibilities,鈥� says optical physicist .
