Scientists Create Photonics Toroidal Vortex Using Conformal Mapping

Posted  by GoPhotonics

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The Future Optical Laboratory led by Academician Zhuang Songlin, USST, witnessed a new breakthrough made by Professor Zhan Qiwen. He reported the experimental observation of a photonic toroidal vortex as a new solution to Maxwell’s equations, generated by the use of conformal mapping.

The resulting light field has a helical phase that twists around a closed loop, leading to an azimuthal local orbital angular momentum density. The preparation of such an intriguing state of light may offer insights for exploring the behavior of toroidal vortices in other disciplines and find important applications in light-matter interactions, optical manipulation, photonic symmetry and topology, and quantum information. The research won support from the National Nature Science Foundation of China (NSFC).

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. A standard vortex is an eddy in a liquid or gas, like a whirlpool. 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. The flow of energy swirls as the ring moves.

Optics researcher Qiwen Zhan 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 Zhan, of the University of Shanghai for Science and Technology. “That’s kind of cool.” Zhan 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.

Click here to read the article titled, "Toroidal vortices of light".