by Paul Arnold, Phys.org

edited by Lisa Lock, reviewed by Robert Egan

In a breakthrough for next-generation technologies, scientists have learned how to precisely control the behavior of tiny waves of light and electrons, paving the way for faster communications and quantum devices.

Controlling light at the smallest scales is crucial for creating incredibly small, fast and efficient devices. Instead of bulky wires and circuits, we can use light to transmit information. One challenge of this approach is that light, with its relatively large wavelength, is not easily confined to small spaces.

However, in a study published in the journal Light: Science & Applications, researchers have developed a method to control tiny waves of light and electrons called Dirac plasmon polaritons (DPPs).

Unlike standard light, DPPs can squeeze into tiny spaces that are hundreds of times smaller than their natural wavelength. This means light can be confined and guided in devices at the nanoscale. In this new research, the scientists demonstrated how they controlled DPPs in the terahertz (THz) frequency range. This region is situated between microwaves and infrared light in the electromagnetic spectrum and is a largely underexplored part of the light spectrum.

The research team was able to control these waves by using a special class of nanomaterials called topological insulators (TIs). TIs are unique because their interior behaves as an electrical insulator while the surface acts as a conductor. Specifically, researchers worked with an advanced material called epitaxial Bi₂Se₃. They arranged tiny strips of this material side by side with gaps between them. Adjusting the gaps had two important consequences.

First, they were able to tune or control the wavelength of the waves, making it about 20% shorter. Second, they extended the attenuation length by more than 50%. This is the distance waves can travel before they lose a significant amount of energy. These two achievements addressed the main challenges of using DPPs (higher momentum than a regular light beam, and they lose energy quickly), making them more practical for real-world applications.

"Our results demonstrate that it is possible to customize the spectral response of Bi₂Se₃-based THz resonators by adjusting the gap. This knowledge can be adopted as a design strategy for the implementation of TI-based architectures," wrote the researchers in their study.

This breakthrough in controlling light waves could lead to the creation of adjustable and energy-efficient THz devices. THz waves can carry more data than current Wi-Fi or 5G, which means lightning-fast downloads and a more secure network. The technology could also create clearer, safer medical imaging and provide the building blocks for more powerful quantum computers.

More information: Leonardo Viti et al, Tracing terahertz plasmon polaritons with a tunable-by-design dispersion in topological insulator metaelements, Light: Science & Applications (2025). DOI: 10.1038/s41377-025-01884-0