Topology helps build more robust photonic networks
Researchers at Penn Engineering draw insights from topology to help drive promising, light-based technological advances in computing and communications.
2 min. read
Penn-led researchers have shown that multiple, information-carrying light signals can be safely guided through chip-based, reconfigurable networks using topology, the esoteric branch of mathematics that says donuts and mugs are identical.
Because topological properties remain stable even when objects are deformed—hence the field equating mugs and donuts, since both have one opening—the novel advance could help make light-based technologies for computing and communications more powerful and reliable.
(From left) Xilin Feng, Liang Feng, and Tianwei Wu developed a microring array that allows multiple beams of light to travel simultaneously, protected by topology.
(Image: Sylvia Zhang)
“We already knew how to guide light using topology,” says Liang Feng, professor in materials science and engineering (MSE) with a secondary appointment in electrical and systems engineering (ESE) at Penn’s School of Engineering and Applied Science and senior author of the study, published in Nature Physics. “But we had never been able to guide multiple, concurrent signals before.”
That opens the door to building networks of chips that communicate using light while taking advantage of the robustness topology provides. “Signals guided by these principles can be extremely reliable,” says Feng. “It’s like building a highway for light where even large potholes have no effect on traffic—it’s as if the defects simply aren’t there.”
Despite their remarkable stability, topological photonic systems have long faced a key limitation: Each protected pathway could carry only a single stream, or “mode,” of light. In effect, the system functioned like a single-lane road, restricting how much data could travel at once.
The new breakthrough came from a theoretical insight into how different “pseudo-spin” states of light interact within the system. By carefully designing the way those states couple at the boundary between regions of the lattice, the researchers realized they could create conditions where several protected channels would appear at the same time, in the same location.
“In conventional topological systems, each interface usually supports only one protected mode in a propagation direction,” says Tianwei Wu, a postdoctoral fellow in ESE and co-first author of the study. “We found that by engineering the coupling between these states, it’s possible to create multiple topological channels along the same pathway.”
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