Scientists have discovered a new form of light that is quite different from all other known forms. Prior to this discovery, it was generally accepted that light in all forms has an angular momentum that is a multiple of Planck’s constant, which is the measurement used to set the scale of quantum effects. The photons (or particles of visible light) in the newly discovered form of light have an angular momentum which measures just half the value of the constant, which translates into a staggering discovery in the world of quantum physics.
A multidisciplinary team of scientists from the Trinity College Dublin’s School of Physics and the CRANN Institute (also at Trinity College) made the discovery, which could fundamentally change how light is studied and how its nature is understood. Kyle Ballantine, a recent PhD graduate, and Paul Eastham, a professor in the School of Physics, worked alongside John Donegan, a professor at CRANN, to unlock the information that could revolutionize our understanding of how light functions. The new form of light, whose photons measure only half the angular momentum as the constant, demonstrates a tiny difference in scale, but an enormous difference when it comes to its impact on the scientific world.
“We’re interested in finding out how we can change the way light behaves, and how that could be useful,” Eastham said. “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.”
The research team used an effect discovered in the same institution nearly two centuries ago, and created beams of light in a Mobius strip-like spiral. After analyzing the light beams with theory of quantum mechanics, they team hypothesized that the angular momentum would measure half, and set about to test that theory. And they were right. Each photon measured just one-half of Planck’s constant.
The study results were recently published in the online journal Science Advances.