Soon, after the International Yoga Day, several researchers from institutions in Spain and the USA have concluded that light can twist too. This new property of light is known as self-torque since an external agent does not cause this noticed torque effect in light. The property is displayed by laser beams that can twist themselves and spin harder and faster along their path. Interestingly, no theory in human history has ever predicted or even suggested a property of light known as self-torque.
To produce the twisting laser beam, scientists made use of a special kind of light that has an orbital angular momentum. An orbital angular momentum can be given to a beam of light when it is made to pass through a seashell-shaped lens. The light comes out looking like a helix spiraling or corkscrewing around a central point and is known as a vortex beam. If this vortex beam falls on a surface, it appears like a donut.
As you can see in the image above, the red beam of light shown is a vortex beam. What is unique about a vortex beam is that when it encounters a nano-sized particle in its path, it will make the particle spin like a planet around a star.
Coming back to the topic, a group of scientists decided to make vortex beams in a region of the electromagnetic spectrum known as extreme ultraviolet. The image below shows an electromagnetic spectrum, which is a range of frequencies of electromagnetic radiation, and the extreme ultraviolet region that lies between the high-energy X-rays and the ultraviolet rays.
While experimenting, the team fired two red laser beams at a cloud of argon gas. The red laser light beam liberated the electrons from the argon. These electrons traveled alongside the laser and gained excess energy. When these electrons collided again with the argon atoms, they released their additional energy as extreme ultraviolet photons with an orbital angular momentum. Consequently, the two lasers joined and emitted a kind of vortex beams from the other side of the argon cloud.
The researchers then questioned what would happen if the red laser beams had different orbital angular momentum speeds and were out of sync with each other by a very tiny fraction of a second. Simulations then showed that the beam produced as a result of this looked like a corkscrew and gradually twisted at an angle. When the beam struck a surface, it appeared like a crescent moon. So, what exactly happened? The beams that came out of the argon cloud were such that the single photon at the front of the beam was orbiting around its center at a much slower rate than a single photon at the back of the beam. Hence, the name self-torque was derived.
We live in a fascinating time where we have captured an image of a black hole and now discovered a new property of light. It is crazy how scientists themselves are not sure of the many useful applications this discovery might have. In my opinion, this discovery has countless applications. One of these applications might include using this property of light to improve our communications technology. Hopefully, it will also shed light on the puzzling mysteries of the universe as only a few systems in our universe display self-torque. Most notably, two black holes revolving around each other can self-torque.
To conclude, I am sure that with our new and better understanding of light, our wildest imaginations will surely come true soon. So, keep reading!!! And continue to speculate, innovate, till you constipate!