Get best of the week

How "swirling light" got into optical networks

American engineers have developed a laser system that encodes data using the orbital angular momentum of a light wave. More information about the project and analogues is under the cut.


/ Unsplash / Reid Zura

What is meant by swirling light


“Ordinary” light has a flat wavefront - this is the surface to which the wave process has reached at the current time. In swirling light, the wavefront is helicoidal - its phase plane rotates with a corkscrew in the direction of wave propagation, therefore it has an orbital angular momentum ( Orbital Angular Momentum, OAM ). This parameter determines the degree of twist and depends on the direction in which the wavefront screw moves. Moreover, its value can be arbitrarily large.

The orbital angular momentum has a large "information capacity", so it is well suited for building communication systems. Data is encoded by changing the direction of rotation (clockwise or counterclockwise) and the swirling force. This approach increases network bandwidth and reduces the number of errors in the transmission of information. Research in this area has been ongoing since at least 1995 . However, the process of quickly switching between OAM states is still a non-trivial task.

It was possible to solve it by a group of American engineers from Pennsylvania and Northeastern Universities, as well as Duke University. To switch between the orbital angular momentum, experts developed a laser system with an annular waveguide.

How does a “twist” system work


Inside the annular waveguide is a series of special partitions. They scatter the light moving along the ring, outside the waveguide - perpendicular to the plane. Engineers can influence the OAM of the scattered light by changing the direction of the beam. The developers say that if you add a light amplifier to the system, this will increase the number of available orbital angular moments. It will allow you to modify the brightness, which will play the role of another variable.

Fresh materials in our blog:


In the future, the technology will find application in the production of more efficient optical chips. But while she is not ready to go beyond the laboratory. First, specialists need to design a laser that can switch between OAM states in a few picoseconds. Then, issues related to reliable transmission of angular momentum will be solved and error correction protocols created.

To use the technology in large-scale fiber-optic networks, the cables themselves will also have to be replaced - standard links cannot transmit swirling light. Experts from Boston University spoke about this feature back in 2013. Then they suggested starting the replacement with cables connecting the servers in the data centers (since they are relatively short).

Who else works in this area


In 2016, a research group from the University of Vienna transmitted data using swirling light to a distance of 143 km. To do this, they used “spiral phase” mirrors, which twisted the photons to quantum numbers (characterize the state of microscopic objects) in excess of 10 thousand. As a result, the accuracy of wavefront formation increased.


/ Unsplash / Dollar Gill

Another project - in 2017, Harvard engineers presented a metasurface that twists light into a spiral or corkscrew. It is expected that it will increase the speed of data transmission through atmospheric optical communication lines.and can become one of the key components for organizing quantum networks. Engineers from the University of Melbourne (RMIT) are

also working on technology for transmitting data using twisted light . One of the key components of their device is an antimony telluride film . It is needed for the generation of surface plasmon polaritons — collective excitations caused by the interaction of photons and electron vibrations. These plasmon polaritons act as information carriers.

So far, new technology is being tested in the walls of a university laboratory. But the developers say that it can enter the market in the next two years. In the future, RMIT's engineering system will become part of quantum Internet.

- :

More articles:


All Articles