Scientists have proposed a theoretical way that light could be slowed down to a complete stop, using something called “exceptional points”.
Published in Physical Review Letters, the authors describe in their study how previous methods included using a cloud of ultracold atoms of sodium to slow light down to speeds approaching zero, but not quite there.
Their method, however, involves using a waveguide – a structure that guides waves in other words, like a tube – to create exceptional points. These are regions where two complex wavelength patterns meet and merge.
What does that mean exactly? Well, we know that light is a wave (most of the time), and these waves constantly change their shape depending on what they’re moving through.
As Live Science notes, if you tune the properties of a container, you can collapse one of light’s complex waves with its mirror twin. Essentially, they cancel each other out. And the point at which that happens is called an exceptional point.
“In this work, we disclose the relation of the stopped light effect with the phenomenon of [the] exceptional point,” the researchers, Tamar Goldzak and Nimrod Moiseyev from the Israel Institute of Technology and Alexei Mailybaev from the Institute for Pure and Applied Mathematics in Brazil, wrote in their paper.
Exceptional points have been shown to have some weird physics before, such as causing lasers to switch on despite energy seemingly being taken away. Sending two wave modes past an exceptional point was described as “driving a car into an icy two-lane tunnel, in which one slides around wildly, but from which one always comes out on the correct side of the road.”
According to this latest paper, in theory, you can cause beams of light to stop moving completely at an exceptional point by changing their properties. The light can then move again when the properties are reversed.
This research is, right now, theoretical. But it could open some interesting avenues for so-called “slow-light applications”, useful for things like telecommunications. And the researchers said the method could apply not just to light waves, but other waves like sound too.