A team of researchers from Spain and the USA has found a new property of light - "self-torque".
In their article published in the journal Science, the researchers describe how they discovered the new property and also talk about its possible uses.
Scientists have long known about the properties of light such as wavelength. More recently, they discovered that light can also be twisted - that is, have angular momentum. Beams of light with highly structured angular momentum are said to have orbital angular momentum and are called "vortex beams". They are a spiral moving around the center, and when the beam hits a flat surface, the vortex beams take the shape of a donut.
In the new work, the scientists examined such rays in a context in which no one had done it before. The experiments involved firing two lasers into an argon cloud, causing the beams to overlap. As a result, they connected and exited as one beam from the other side of the argon cloud. The result is a vortex beam.
The researchers then wondered what would happen if the lasers had different orbital angular momentum and if they were slightly synchronized. The result is a corkscrew-like beam with a gradually changing angle of rotation. And when the beam hit the flat surface, it looked like a crescent moon. The researchers noted that this was because a single photon at the front of the beam was spinning around its center more slowly than the photon at the outside of the beam.
Scientists quickly dubbed the new property "self-torque". It turned out that this is not only a recently discovered property of light, but also one that was never even predicted. Also, scientists talked about the prospects for the application of their discovery. This could lead to the development of new devices that use the manipulation of nanoscale materials, they said.
Nikita Shevtsov