Physicists from Trinity College Dublin’s School of Physics, have discovered a new form of light, which is expected to affect our overall understanding of light.
One of the characteristics of the beam of light which can be measured is the so-called angular momentum. Until now it was thought that in all types of light the angular momentum is a multiple of Planck’s constant (physical constant and the smallest unit of space that determines the scale of the quantum effects).
PhD graduate Kyle Ballantine and Professor Paul Eastham, both from Trinity College Dublin’s School of Physics, along with Professor John Donegan from CRANN, have demonstrated a new form of light in which the angular momentum of each photon is only half of the normal value.
“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.”
The study focuses on nanophotonics, which is the behavior of light at nanometric level. A beam of light is characterized by a color (wavelength) and angular momentum (polarization). When a light beam is moving in a straight line, it is actually rotate around its own axis in the direction of movement – something that is characteristic of all the electromagnetic waves.
If you’ve heard of polarization, meaning the direction of this angular momentum. It is this property of light used in 3D cinema where the light coming from the display is polarized differently for left and right eye.
If you’ve heard of polarization, it is connected with the direction of this angular momentum. It is this property of light used in 3D cinema where the light coming from the display is polarized differently for left and right eye.
To make the discovery, scientists used an effect discovered in the same institute almost 200 years ago. In an experiment with crystals a beam of light becomes an empty cylinder. Based on this, the researchers used specially designed device to measure the angular momentum. For the first time they measured the variations caused by quantum effects.
Theoretical physicists from the 80s speculate how quantum mechanics works on particles that are free to move in only two of the three dimensions. They found that it would reveal new opportunities, including particles with quantum numbers much smaller than expected.
The discovery will influence the study of light, as well as in areas such as optical communications.
But before we get too exciting from this new form of light, another group of scientists should replicate and validate this work to make sure it wasn’t just a chance happened only once.
The results have been published in Science Advances.