Mini-vortices of light could carry huge amounts of data

Researchers have developed a quasi-crystal-like structure that generates mini-vortices of light that can carry enormous amounts of data. It is composed of metallic nanoparticles very precisely arranged to generate any type of vortex — by interacting with a beam of light contained in an electric field. When applied to optical fibers, the structure could carry 8 to 16 times more information than current systems.

Information transmission in the digital age relies largely on photonic data encoding. Optical fibers are currently the most used infrastructure for this purpose. However, growing demands for information capacity require the development of systems that can encode and transport larger volumes of data.

Light vortices have been explored for several years in order to optimize the photonic transport of information. These vortices aim to manipulate topological defects in light so as to control the way it is reflected and the information it carries. While some topological defects form spontaneously and are ubiquitous in nature, others can arise from symmetry in the structure of the materials with which light interacts. This affects the shape and structure of the resulting vortex.

For example, materials whose structure is arranged in squares (or tiles) generate single vortices, while hexagonal patterns generate a double vortex and so on. More complex swirls require at least octagonal structures. However, generating wormholes complex enough for data encoding poses a significant challenge.

The new design from the team at Aalto University (in Finland) overcomes these challenges and could generate any type of vortex. “ This research focuses on the relationship between vortex symmetry and rotationality, i.e. which types of vortices can be generated with which types of symmetries. Our quasi-crystal design is halfway between order and chaos », Explains in a press release Päivi Törmä, who led the study, published in the journal Nature
Communications.

Towards new generation telecommunications infrastructures

The design is a quasi-crystal composed of metal nanoparticles. Like classical crystals, quasicrystals have a discrete diffraction spectrum, but unlike the former, their structure is not periodic. To create their quasi-crystal, the researchers manipulated 100,000 metal nanoparticles whose diameter does not exceed one hundredth of a human hair. The assembly interacts with a beam of light in a controlled electric field.

The structure of the generated light vortex is comparable to a cyclone. It has a calm, dark “eye” in the center that is surrounded by a ring of bright light made up of streams oriented in different directions. To identify the optimal arrangement for generating the complex vortices, the team took a counterintuitive approach of identifying the points where particles interact least with the electric field.

« An electric field has hot spots of strong vibration and points where it is virtually inactive. We introduced particles into the dead spots, which deactivated everything else and allowed us to select the field with the most interesting properties for applications “, explains Jani Matti Taskinen, co-lead author of the study.

This technique would thus make it possible to adjust the patterns so as to generate complex vortex structures according to needs. “ Our quasicrystal design uses group theory to determine electromagnetic field nodes, where plasmonic nanoparticles are positioned to maximize gain », Write the experts in the document. Group theory is a calculation method for predicting the type of deformation that the structure of a material might undergo.

These complex vortices would make it possible to store large volumes of information in a small space. They could be transported through optical fibers and then decompressed once they arrive at their destination. According to the team’s estimates, these fibers would, in the best case scenario, allow 8 to 16 times more information to be transported than current ones.

This approach could pave the way for a new generation of telecommunications infrastructure. However, the necessary improvements to the concept for practical applications will require several more years of research, the scientists said.

Source : Nature Communications