Skyrmion topology makes long-distance optical communications more robust
New work will help advance the development of more reliable free-space networks The post Skyrmion topology makes long-distance optical communications more robust appeared first on Physics World .
Researchers at the University of the Witwatersrand in Johannesburg, South Africa, have developed a novel method for transferring information through the atmosphere using the unique property of light topology. This breakthrough could lead to more reliable long-distance optical communications, including space-based ones, and help connect remote and underserved communities worldwide.
Their findings are detailed in two studies, one classical and one quantum-based, both of which show that the topology of light can remain intact even when exposed to the severe distortions caused by atmospheric turbulence.
The researchers utilized a fundamental concept in optics: creating an optical topological structure called a skyrmion in a light field and testing its resilience when passing through a distorting environment. Skyrmions are quasiparticles with a knot-like, two-dimensional structure, first observed in magnetic materials but later found in electromagnetic fields, including light waves.
These structures are created by twisting the polarization or spin vectors of light in space, ensuring that every polarization is represented exactly once, twice, three times, and so on, with the count being the skyrmion number.
In a real-world test, the researchers generated optical skyrmions with skyrmion numbers of 1, 2, and 3 using laser light with a 532 nm wavelength. These skyrmions were then sent through a 270-meter-long free-space optical link on Wits' Braamfontein campus in Johannesburg. The team measured the skyrmions' topology using a Stokes polarimetry setup and found that the skyrmion number remained robust across various atmospheric conditions, from calm mornings to intense distortions during midday.
In a second study, the team created a skyrmion with a skyrmion number of 1 through the inherent correlations between two photons entangled in their optical angular momentum (OAM). Despite the individual photons' OAM being easily lost in distorting environments, the skyrmion maintained a topological number close to 1. This suggests that the topological number is not influenced by modal crosstalk or the spreading of an individual photon's OAM caused by turbulence.
Both studies demonstrate that optical topology can serve as a robust carrier of information in various communication and information-processing scenarios. Topology is a concept prevalent throughout physics, often providing a form of physical protection against external disturbances. However, in optics, the robustness of optical topology is not guaranteed by any particular underlying physical mechanism.
This research aims to address this fundamental question and explore the potential practical value of topology in real-world optical sensing and communications, where rapidly varying distortions are common.
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