Scientists Say They Have Discovered a New Form of Light

Posted on May 18, 2016

Physicists at Ireland's Trinity College Dublin says they have discovered a new form of light. One of the measurable characters of light is angular momentum. In all forms of light the angular momentum was until now expected be a multiple of Planck's constant. Particles of light (photons) rotate around their axis as they travel through space. The researchers demonstrated an experiment where the angular momentum of each photon takes only half of this value.

PhD graduate Kyle Ballantine and Professor Paul Eastham from Trinity College Dublin's School of Physics passed light through crystals to generate beams of light with a screw-like structure. Using a specially constructed device they were able to measure the flow of angular momentum in a beam of this light. The experiments revealed a tiny shift - one-half of Planck's constant - in the angular momentum of each photon.

Eastham says in a statement, "We're interested in finding out how we can change the way light behaves, and how that could be useful. 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."

Eastham explained the discovery to CNN. He says, "It's a bit like a tiny, light merry-go-round at a playground. It goes round and round, which is more or less they way people understood light to work. We thought it was impossible for a photon to send you halfway round, but it turns out, it's not."

Physics World also has an article on the discovery with an image illustrating half-twists or half-integer angular momentum.

The researchers say the discovery could lead to improved security in optical communications. CNN says, "the nature of these newly found photons are by nature harder to crack."

A research paper on the study was published here in the journal, Science Advances.