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The power of light
September/October 2009
by Bruce Fellman
It turns out that light is like magnetism: it can pull or push. Light beams can either attract or repulse each other, and this discovery, says the electrical engineer who made it, "opens the way to creating the communications devices of the future—devices that replace electrons with photons."
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Communications devices that use light instead of electricity should convey information faster.
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In 2008, Hong Tang and two colleagues showed that beams of infrared light traveling in nanoscale silicon "wires," called waveguides, could exert an attractive force on each other when they were brought extremely close together. (The force exists only at nanoscale distances, less than two-millionths of an inch, and not when you mingle the beams of two flashlights or laser pointers.) The attraction was strong enough to pull open minuscule switches on silicon chips. But there was no way to push the switches off.
Now, Tang's group has succeeded in producing a repulsive force, by altering the route of the waveguides and setting the light beams out of phase with each other. (The work is featured on the cover of the August issue of Nature Photonics.)
Communications devices that use light instead of electricity should convey information faster, take less energy to operate, and release very little heat—which many electronic devices, from smartphones to network cards, produce at levels high enough to shorten their life span. Tang is now working on refining the push-pull process, but he is a long way from building a product. "There's nothing yet—otherwise, I'd be rich." 
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