|To prevent microwaves passing through it from reflecting backward, a new 'metamaterial' uses antennas of alternating orientations (top) that are connected by amplifier circuits (bottom).|
Today’s optical networks keep light from reflecting backward with devices called isolators, which are made from exotic materials like yttrium indium garnet and work only when a magnetic field is applied to them, which makes them bulky. But since isolators absorb light particles — photons — to prevent them from scattering backward, they also diminish the strength of forward-moving optical signals.
In this week’s Proceedings of the National Academy of Sciences, researchers at MIT, Zhejiang University in China, and the University of Texas at Austin describe a new “metamaterial” that keeps photons moving in only one direction, rechanneling the stragglers rather than simply absorbing them. Although the prototype is large, it doesn’t require the application of a magnetic field, so it could, in principle, yield optical components much smaller than today’s isolators. Moreover, building a chip-scale version of the metamaterial would require no materials more exotic than the metals already used in microprocessors, reducing manufacturing costs.