Researchers at King’s College London in the U.K. have successfully demonstrated control over the direction of movement of electromagnetic waves in waveguides through the use of circular polarization to send waves in a single direction along a metal surface. Their achievement marks the first time unidirectional waves were controlled with these methods and could have strong implications for optical telecommunication and information processing technologies.
By focusing circularly polarized light containing spinning photons on a metal nanostructure, Professor Anatoly Zayats of the Department of Physics at King’s College and his team were able to influence the electrons in the nanostructure to move clockwise or counterclockwise in circles depending on the direction of the photons’ spin. Bringing this structure close to an optical waveguide or a metal surface influences the direction of wave travel within these materials; reversing the polarization direction of the light changes the direction of the wave.
“Wave interference is a basic physics phenomenon, known for many centuries, with myriad applications. When we observed that it can lead to unidirectional guiding when spin carrying photons are used, we could not at first believe that such a fundamental effect had been overlooked all this time,” Zayats said. “We will now work on developing its applications in nanophotonics and quantum optics.”
“[The] phenomenon holds promise for spin sorting of photons, processing of polarization encoded information and much more,” Francisco Rodríguez Fortuño, a Ph.D student and member of the research team, said.