'Exceptional Points' Could Stop Light Waves in their Tracks

[Judi Lynn]

By Rafi Letzter, Staff Writer | January 31, 2018 04:01pm ET

Light moves fast. That's kind of the whole point of light, at least the way most people think about it. Light shoots through the 93 million miles between Earth and the sun in just 8 minutes, it carries information all around the world nearly instantly, and its top speed of 186,000 miles per second (300,000 kilometers/s) turns out to be the absolute speed limit of the entire universe.

But there are some physicists interested in turning that trait of light on its head, and slowing it way down. And in a new paper, published Jan. 3 in the journal Physical Review Letters and on arXiv, a team of researchers showed that light could be made to come to an absolute stop at certain "exceptional points."

This isn't the first technique scientists have come up with for slowing down light. Back in 2001, a paper published in the journal Nature (and explained in The New York Times) showed that light could be imprinted on supercooled atoms in such a way that it comes to a complete stop — then jogged by a second pulse of light into continuing along its merry way. [The 18 Biggest Unsolved Mysteries in Physics]

But the technique described in this Jan. 3 paper doesn't rely on supercooled atoms or imprinting light. Instead, it relies on some funny quirks of how waves — including light waves — behave under the unusual circumstances of "exceptional points."

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