Not all light is made equal. Now, a team of physicists has discovered that photons can travel differently to any other light that scientists have seen in the past.
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The team from Trinity College Dublin has been studying the angular momentum of light. As a beam of light travels through space, it propagates forward in a straight line but it can be rotating about the axis along which it travels, like a corkscrew twirling through space. Until now, the angular momentum resulting from that rotation was always thought to be an integer multiple of Planck's constant.
But new experiments by the team show that it's possible for photons to have angular momentum that is half of those values. The team initially predicted the phenomenon using theoretical models, then tested it using specially constructed experimental kit that could twist a light beam by passing it through crystals of material. Ultimately, they found that half-multiples of angular velocity were in fact possible. The research is published in Science Advances.
It's a subtle but interesting finding, though one whose immediate impacts are hard to predict. "What I think is so exciting about this result is that even this fundamental property of light, that physicists have always thought was fixed, can be changed," explained Assistant Professor Paul Eastham, one of the researchers, in a press release. The team does, however, reckon it could find application in light-based communications, to better encode and secure data in light beams.