Researchers in China have unveiled an optical device that can generate and switch between electric and magnetic “vortex” light patterns, a breakthrough that could bolster the reliability of next-generation terahertz wireless communications.
The device produces structured light vortices, known as skyrmions, which are highly stable and resistant to disturbances, making them ideal candidates for encoding information in free-space terahertz pulses. Terahertz waves, which sit between microwaves and infrared light, are increasingly being explored for ultra-fast wireless communications and advanced sensing technologies.
“Our device not only generates multiple vortex patterns in free-space-propagating terahertz pulses but can also switch, on demand, between two modes using the same integrated platform,” said Xueqian Zhang, Corresponding Author and physicist at Tianjin University in a press statement. “Such controllability is essential for real applications, where reliable selection and reproduction of a desired state are crucial for practical information encoding.”
The research, published in the journal Optica, marks the first experimental demonstration of skyrmions that can be switched between electric and magnetic modes. The team achieved this using a nonlinear metasurface, an ultra-thin material patterned at the nanoscale that manipulates light in ways conventional optics cannot.
“Most existing devices can produce only one type of toroidal vortex, and they lack the ability to switch between modes,” said Yijie Shen, co-corresponding author and physicist at Nanyang Technological University. “Our results move the concept of switchable free-space skyrmions toward a controllable tool for robust information encoding. This could inspire more resilient approaches to terahertz wireless communication and light-based information processing.”
To operate the device, near-infrared femtosecond laser pulses with different polarisation profiles are directed onto the metasurface, producing terahertz toroidal light pulses that carry either an electric-mode or a magnetic-mode vortex.
“It’s like using different keys to open different doors,” said Li Niu, first author from Tianjin University. “One light pattern activates the electric mode, another triggers the magnetic mode.”
Jiaguang Han, project leader at Tianjin University, added: “By employing simple optical elements such as wave plates and vortex retarders to control the polarisation of the input laser, we can create a compact device that actively switches between two distinct topological light states.”
The team evaluated performance using an ultrafast terahertz measurement setup, scanning pulses across space and time to reconstruct the evolving field patterns. Fidelity measures confirmed both high purity and reliable mode switching.
Looking ahead, the researchers aim to improve long-term stability, compactness, and efficiency, while extending the system beyond two states to enable richer encoding schemes.
“We hope this work will form a foundation for future terahertz communications and light-based circuits that can generate, switch, and route different signal states in a controlled way,” said Shen.
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