Quantum Light Breakthrough Heralds New Era in Terahertz Technology
November 2, 2025 – Changchun, China — Scientists have achieved a landmark breakthrough in the manipulation of light frequencies using quantum materials, potentially transforming a wide array of technologies ranging from ultrafast electronics to quantum computing and wireless communication.
A research team from the Light Publishing Center at the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CAS), led by Professor Miriam Serena Vitiello, has successfully harnessed the unique properties of topological insulators to produce both even and odd terahertz (THz) frequency harmonics through a process known as high-order harmonic generation (HHG). This achievement opens up new frontiers in terahertz science and technology.
Overcoming Symmetry Limitations in Terahertz Frequency Generation
High-order harmonic generation is a nonlinear optical process that converts light into much higher frequencies, enabling access to electromagnetic spectrum regions otherwise difficult to reach. However, the generation of terahertz frequencies using HHG has long been obstructed by material symmetry constraints. Most conventional materials exhibit high symmetry, restricting harmonic generation predominantly to odd harmonics—frequencies that are odd-number multiples of the initial light source.
Graphene, while a promising candidate in HHG studies, is limited by its perfect symmetry that allows only odd harmonic generation. Even harmonics, which are essential for broadening the applicability of HHG in real-world devices, have remained elusive.
Topological Insulators: Breaking New Ground
The team’s efforts focused on topological insulators (TIs), exotic quantum materials characterized by insulating interiors and conductive surfaces. These materials display remarkable quantum phenomena due to strong spin-orbit coupling and unique time-reversal symmetry properties.
Although theoretical models had suggested that TIs could support a richer variety of harmonic generations, conclusive experimental proof had been lacking—until this study.
Designing Quantum Nanostructures for Amplified Light
By embedding ultrathin layers of bismuth selenide (Bi₂Se₃) and van der Waals heterostructures of indium-bismuth selenide ((InₓBi₁₋ₓ)₂Se₃) into intricately designed split ring resonators—nano-engineered structures known to intensify electromagnetic fields—the researchers managed to amplify incoming terahertz light dramatically.
This setup allowed them to observe HHG simultaneously producing both even and odd harmonics within the terahertz range, notably at frequencies between 6.4 THz (even harmonics) and 9.7 THz (odd harmonics). The results demonstrated how the symmetrical bulk interior and asymmetric surface states of the TIs each contribute to harmonic generation, confirming quantum effects theorized for years.
Implications for Future Technologies
This pioneering work substantiates longstanding theoretical predictions and sets a foundation for creating novel, compact terahertz light sources and sensors. The ability to generate and manipulate both even and odd terahertz frequencies with high efficiency opens new avenues for miniaturized ultrafast optoelectronic components.
Such terahertz technologies promise to revolutionize a variety of fields. In wireless communication, they could support ultra-high-speed data transmission. Medical imaging could benefit from enhanced resolution and sensitivity, while quantum computing architectures might utilize these advances for faster, more reliable qubit manipulation.
Moreover, the successful integration of topological insulator materials into functional nanostructures highlights the growing potential of quantum materials to drive technological innovation, addressing increasing demands for smaller, faster, and more energy-efficient devices.
About the Study
Details of the breakthrough are presented in the paper “Second and third harmonic generation in topological insulator-based van der Waals metamaterials”, published in Light: Science & Applications (2025), authored by Alessandra Di Gaspare, Sara Ghayeb Zamharir, Craig Knox, Ahmet Yagmur, Satoshi Sasaki, Mohammed Salih, Lianhe Li, Edmund H. Linfield, Joshua Freeman, and Miriam S. Vitiello.
For further information and media inquiries:
Light Publishing Center
Changchun Institute of Optics, Fine Mechanics and Physics, CAS
ScienceDaily Article
This discovery signals a major step forward in our ability to manipulate light and quantum materials, promising transformative impacts across science and technology in the years ahead.
