Scientists Unlock a Hidden Side of Light That Could Transform Technology
Changchun, November 6, 2025 — A groundbreaking advance in light-based technology has opened up a previously inaccessible segment of the electromagnetic spectrum, potentially revolutionizing wireless communication, imaging, and quantum computing. Researchers at the Changchun Institute of Optics and the Light Publishing Center have successfully harnessed exotic quantum materials to generate both even and odd terahertz harmonics, breaking longstanding symmetry barriers in light behavior.
Breaking Through the Symmetry Barrier of Light
High-order harmonic generation (HHG) is a sophisticated optical technique that converts low-frequency light into much higher frequencies. It has allowed scientists to probe spectral regions that are typically out of reach. However, extending this method effectively into the terahertz (THz) frequency range has posed a formidable challenge. This is largely due to the inherent symmetrical properties of many materials, which restrict the process primarily to odd harmonics—odd multiples of the original frequency.
For instance, graphene, heralded for its promising light-conversion potential, is limited by its structural symmetry, producing only odd harmonics. Even harmonics—essential for creating a fuller light spectrum and enabling more versatile applications—have thus remained experimentally elusive in the terahertz domain until now.
Harnessing Quantum Materials: The Role of Topological Insulators
Led by Professor Miriam Serena Vitiello, the research team has employed topological insulators (TIs)—a class of quantum materials characterized by insulating interiors and electrically conductive surfaces—to overcome this barrier. TIs possess unconventional quantum attributes, including strong spin–orbit coupling and time-reversal symmetry effects. While theoretical models hinted at their potential for complex harmonic generation, clear experimental validation had been absent.
Leveraging these unique material properties, the team generated new, controllable light frequencies in the terahertz range. This marks one of the first experimental confirmations that TIs can facilitate both even and odd harmonic generation, thereby “unlocking” a hidden side of light.
Amplification Through Nanostructures
To enhance the incoming light’s interaction with the materials, the team engineered nanoscale devices known as split ring resonators (SRRs). These were fabricated alongside thin films of bismuth selenide (Bi₂Se₃) and layered van der Waals heterostructures composed of (InₓBi₁₋ₓ)₂Se₃. The SRRs amplified the electromagnetic fields effectively, enabling the observation of HHG at frequencies spanning from 6.4 THz (even harmonics) to 9.7 THz (odd harmonics).
This frequency up-conversion showcases the interplay between the symmetrical bulk and the asymmetrical surface states of the topological insulators, offering vital insight into the relationship between material symmetry and light behavior at terahertz frequencies. This breakthrough substantiates long-standing theoretical predictions and lays the groundwork for compact, tunable terahertz light sources.
Implications for Future Technology
The ability to generate a broader spectrum of terahertz frequencies using compact and material-engineered systems opens multiple doors for real-world applications. Terahertz light sources could become smaller, more tunable, and more efficient, greatly benefiting technologies that rely on high-speed data transmission, medical and security imaging, and emerging quantum devices.
In particular, the research paves the way for ultrafast optoelectronic components and sensors that harness the unusual quantum states of topological insulators. The implications extend into the realms of nanoscale light–matter interactions, potentially transforming photonic computing, quantum information processing, and beyond.
Published Study and Acknowledgements
The full details of this research are published in the journal Light: Science & Applications under the article titled “Second and third harmonic generation in topological insulator-based van der Waals metamaterials” by Alessandra Di Gaspare and colleagues, dated September 22, 2025. DOI: 10.1038/s41377-025-01847-5
About the Changchun Institute of Optics
The Changchun Institute of Optics is recognized globally for advancing photonics and quantum materials research—driving innovations that push the boundaries of modern technology.
For continuous updates on breakthroughs in science and technology, subscribe to SciTechDaily and follow our channels on Facebook, Twitter, and LinkedIn.
Contact: Light Publishing Center, Changchun Institute of Optics, November 6, 2025
