A team comprised of researchers that are affiliated with different institutions in Spain and the US has revealed that it has found a new property of light. The property that has been discovered is that of self-torque. The paper published in the journal Science, explains how the group was able to identify the new property and find possible applications for it.
Scientists have been aware of properties of light such as wavelength. Recently, researchers also discovered that the light could be twisted – a property known as angular momentum. Beams featuring highly structured angular momentum are known to possess orbital angular momentum (OAM) and are known as vortex beams.
These vortex beams have a shape of a helix surrounding a common center, and upon striking a flat surface that becomes doughnut-shaped. During the experiments, when self-torque was discovered – that the researchers were carrying out, they were working with OAM beams when they experienced light behaving in a way that had never been known before. The experiment was about firing two lasers at a cloud of argon gas. By doing so, the team forced the beams to overlap, join together, and then emitted as a single beam from the other side of the cloud of argon gas. The resulting beam was a kind of vortex beam.
The researchers then wondered what would happen if the beams being fired had varying orbital angular momentum and if they were slightly out of sync. This led to the creation of a beam that looked similar to a corkscrew with a slowly changing twist. Upon striking a flat surface, the beam looked like a crescent moon. The researchers also noted that when looked at another way, a single photon was found at the front of the beam that was orbiting around its center slower than a photon at the back of the beam. The researchers have dubbed this new property as self-torque.
Self-torque is not just a newly discovered property of light, but it is also the kind of property that had never been predicted. According to researchers, using this technique; modulation of the orbital angular momentum of light similar to modulation of frequencies in communications equipment could be possible.
