Quantum materials enable an ultrafast, ultrathin, tunable terahertz device

Terahertz devices have applications in biomedicine, imaging, sensing, and communication. However, rapidly tuning their transmission currently requires both metallic passive components and a semiconductor for control, resulting in complex, bulky designs.

Mishra et al. designed and fabricated an ultrathin, ultrafast, tunable terahertz device based on cadmium arsenide. Cd₃As₂ is a topological Dirac semimetal — a three-dimensional quantum material with very high electron mobility and ultrafast carrier dynamics. These properties allowed the researchers to optically modulate the metallic and dielectric properties of Cd₃As₂ to tune the device on a picosecond timescale, eliminating the need for an additional semiconductor layer.

The authors patterned thin Cd₃As₂ films with a periodic hole array, structures that exhibit enhanced optical transmission, to create geometric resonances in the material. These resonances can be switched on and off at a speed of 40 gigahertz by varying the optical energy delivered to the films. The tuning was achieved at room temperature with low optical energy. The material’s kinetic inductance at room temperature granted further control of the resonance frequency.

“This work highlights how ideas from topological quantum materials can translate into very practical terahertz devices that are ultrathin, ultrafast, and energy efficient,” said author Sobhan Subhra Mishra. “Cadmium arsenide offers the environmental stability and scalability needed for real-world deployment, while still retaining the ultrafast carrier dynamics associated with Dirac fermions.”

The results suggest that next-generation terahertz devices could be based on topological materials. This device could be used to develop switches, filters, and modulators for spectroscopy, as well as short-range wireless links. Next, the authors plan to reduce the energy loss of their device.

Source: “Ultrafast active 3D dirac terahertz metadevice,” by Sobhan Subhra Mishra, Darren Chin Yao Lim, Aolong Li, Ietro Pang Teng Chen, Thomas Tan CaiWei, Baolong Zhang, Yogesh Kumar Srivastava, Faxian Xiu, and Ranjan Singh, APL Engineering Physics (2026). The article can be accessed at https://doi.org/10.1063/5.0313752 .