A new metasurface lets scientists flip between ultra-stable light vortices, paving the way for tougher, smarter wireless communication.
Scientists have developed a new optical device capable of producing two different types of vortex-shaped light patterns: electric and magnetic. These unusual light structures, called skyrmions, are known for their exceptional stability and resistance to interference. Because they hold their shape so reliably, they are strong candidates for carrying information in future wireless communication systems.
“Our device not only generates more than one vortex pattern in free-space-propagating terahertz pulses but can also be used to switch, on demand, between two modes using the same integrated platform,” said corresponding author Xueqian Zhang from Tianjin University. “Such controllability is essential for real applications, where reliable selection and reproduction of a desired stated are crucial for practical information encoding.”
Writing in Optica, Optica Publishing Group’s journal for high-impact research, Zhang and his colleagues report the first experimental demonstration of skyrmions that can be actively switched between electric and magnetic forms in toroidal terahertz light pulses. The key to this achievement is a nonlinear metasurface. Metasurfaces are ultra-thin materials patterned at the nanoscale that can manipulate light in ways traditional optical components cannot.
“Our results move the concept of switchable free-space skyrmions toward a controllable tool for robust information encoding,” said co-corresponding author Yijie Shen from Nanyang Technological University. “This work could inspire more resilient approaches to terahertz wireless communication and light-based information processing. This type of control could also enable light-based circuits that generate, switch and route different signal states in a controlled way.”
Programmable terahertz vortices
Terahertz waves are gaining attention as a foundation for next-generation communication and sensing technologies. This research is part of a broader effort to create terahertz light sources that do more than simply emit pulses. The goal is to shape and control those pulses so they can carry information more efficiently.
Toroidal vortices of light have a ring-shaped structure in which the electromagnetic field curls back on itself, forming a stable, donut-like pattern. These shapes are especially appealing because they provide additional ways to encode data. Most existing devices, however, can produce only a single type of toroidal vortex and usually lack the ability to switch between different modes.
To overcome these limitations, the researchers designed an integrated device that can toggle between electric and magnetic toroidal vortex patterns in free-space terahertz pulses. This was accomplished using a nonlinear metasurface made from precisely patterned metallic nanostructures.
When near-infrared femtosecond laser pulses with different polarization patterns strike the metasurface, the device generates distinct terahertz toroidal pulses. Depending on the polarization of the incoming light, the resulting vortex takes on either an electric or magnetic skyrmion structure. The concept is similar to using different keys to unlock different outcomes: one light pattern activates the electric mode, while another activates the magnetic mode.
“The core innovation lies in the nonlinear metasurface that converts shaped near-infrared femtosecond laser pulses into tailored terahertz toroidal light pulses,” said first author Li Niu from Tianjin University, who carried out the experiments.
Project leader Jiaguang Han from Tianjin University added, “By employing simple optical elements such as wave plates and vortex retarders to control the polarization pattern of the input laser, we are able to create a compact device that can actively switch between two distinct topological light states.”
Tracking and validating skyrmion modes
To test how well the device performed, the team built an ultrafast terahertz measurement system that allowed them to observe the light pulse as it traveled through space. Instead of capturing a single image, they recorded the pulse at multiple positions and time points, allowing them to reconstruct how the electromagnetic field evolved.
These measurements clearly revealed the defining features of the toroidal pulses and confirmed the presence of two distinct skyrmion modes. The researchers also used fidelity measurements to assess performance, showing that the device can switch modes reliably while maintaining high purity of each state.
Looking to the future, the team plans to move the technology closer to practical communication applications. This includes improving long-term stability, repeatability, and efficiency, as well as shrinking and strengthening the overall system. They also aim to expand the approach beyond just two modes by adding more controllable states, which would allow even richer and more flexible information encoding.
Reference: “Electric-Magnetic-Switchable Free-Space Skyrmions in Toroidal Light Pulses via a Nonlinear Metasurface” 29 January 2026, Optica.
DOI: 10.1364/OPTICA.578501
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