What about smoke rings

Scientists have created vortex rings of light. The ring’s surface is illustrated in transparent purple, and a hollow core is shown in orange. Rainbow arrows show the rotation of the vortex, and white arrows indicate a type of angular momentum of the light.

Smoke rings are being seen in a new light.

Doughnut-shaped structures called vortex rings are sometimes seen swirling through fluids. Smokers can form them with their mouths, volcanoes can spit them out during eruptions and dolphins can blow them as bubble rings. Now, scientists can create the rings with light.

Smoke rings are being seen in a new light.

A standard vortex is an eddy in a liquid or gas, like a whirlpool (SN: 3/5/13). Imagine taking that swirling eddy, stretching it out and bending it into a circle and attaching it end-to-end. That’s a vortex ring. These rings travel through the liquid or gas as they swirl — for example, smoke rings float through the air away from a smoker’s head. In the new vortex rings, described June 2 in Nature Photonics, light behaves similarly: The flow of energy swirls as the ring moves.

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Optics researcher Queen Khan and colleagues started from a vortex tube, a hurricanelike structure they already knew how to create using laser light. The team used optics techniques to bend the tube into a circular shape, creating a vortex ring.

The light rings aren’t that different from smoke or bubble rings, says Khan, of the University of Shanghai for Science and Technology. “That’s kind of cool.”

Khan is interested in seeing whether scientists could create vortex rings out of electric current or a magnetic field. And further study of the light rings might help scientists better understand how topology — the geometry of doughnuts, knots and similar shapes — affects light and how it interacts with matter.

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CITATIONS

C. Wan et al. Toroidal vortices of light. Nature Photonics. Published online, June 2, 2022. Doc: 10.1038/s41566-022-01013-y.

Emily Conover

About Emily Conover

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Physics writer Emily Conover has a Ph.D. in physics from the University of Chicago. She is a two-time winner of the D.C. Science Writers’ Association News brief award.