THz-optical converter; THz modulation; reconfigurable antenna.
Researchers from École Polytechnique Fédérale de Lausanne (EPFL) and Harvard University designed a chip that can convert between electromagnetic pulses in the terahertz and optical ranges on the same device. Applications include communication, sensing, spectroscopy, and computing.
The design embeds micron-sized transmission lines into a lithium niobate photonic chip that act like chip-scale radio cables to guide THz waves along the chip. A second structure placed nearby guides optical waves, which enhances interaction and conversion between the two with minimal energy loss.
“In addition to demonstrating the first detection of THz pulses on a lithium niobate photonic circuit chip, we generated THz electric fields over 100 times stronger and increased the bandwidth by a factor of five (going from 680 GHz to 3.5 THz),” said Cristina Benea-Chelmus, head of the Laboratory of Hybrid Photonics at EPFL, in a press release. “We anticipate that the design guidelines we propose will become crucial in future terahertz applications such as high-speed 6G communications, where sensing and ranging will be an essential component of the communication network.” [1]
Researchers from University of Cambridge, Queen Mary University of London, University College London, and University of Augsburg developed tunable capacitors made of graphene that can be used in gold metamaterial resonator arrays to modulate terahertz signals. The tunable capacitors enable the resonance to be shifted without suppressing it. Performance was further improved by designing the device to reflect signals from its back surface.
“By changing the design of the nanoscale gap in any metamaterial relying on a resonator, you can significantly influence the optical response and hence improve modulation efficiency,” said Wladislaw Michailow, a junior research fellow at Trinity College Cambridge, in a release. “The approach we’ve taken here could be applied to many other types of metamaterial-based modulators.”
“This way we were able to achieve a modulation depth of more than four orders of magnitude. This is one of the highest values ever reported in the terahertz range,” said Ruqiao Xia, a PhD graduate from the Cavendish Laboratory at Cambridge, in a release. “The performance of our devices significantly exceeds that of many comparable modulator technologies, and thanks to the use of metamaterials, we can adapt the design for use across the entire terahertz range.” [2]
Researchers from Massachusetts Institute of Technology (MIT), Gwangju Institute of Science and Technology, and University of Michigan developed a reconfigurable antenna that dynamically and reversibly adjusts its frequency range by changing its physical shape through stretching, bending, or compression.
The meta-antenna is composed of a dielectric layer of material sandwiched between two spray-painted conductive layers. A coating of flexible acrylic paint helped prevent it from breaking.
“Usually, when we think of antennas, we think of static antennas — they are fabricated to have specific properties and that is it. However, by using auxetic metamaterials, which can deform into three different geometric states, we can seamlessly change the properties of the antenna by changing its geometry, without fabricating a new structure. In addition, we can use changes in the antenna’s radio frequency properties, due to changes in the metamaterial geometry, as a new method of sensing for interaction design,” said Marwa AlAlawi, a mechanical engineering graduate student at MIT, in a statement. “In order to trigger changes in resonance frequency, we either need to change the antenna’s effective length or introduce slits and holes into it. Metamaterials allow us to get those different states from only one structure.”
The team also built a tool that enables users to design and produce metamaterial antennas for specific applications. They used it to design antennas for several smart devices, including curtains and headphones. Applications include energy transfer in wearable devices, motion tracking and sensing for augmented reality, and wireless communication. [3]
[1] Y. Lampert, A. Shams-Ansari, A. Gaier, et al. Photonics-integrated terahertz transmission lines. Nat Commun 16, 7004 (2025). https://doi.org/10.1038/s41467-025-62267-y
[2] R. Xia, N.W. Almond, W. Tadbier, et al. ‘Achieving 100% amplitude modulation depth in the terahertz range with graphene-based tuneable capacitance metamaterials’, Light Sci Appl 14, 256 (2025) https://doi.org/10.1038/s41377-025-01945-4
[3] M. AlAlawi, R. Zheng, S. Ahn, et al. Meta-antenna: Mechanically Frequency Reconfigurable Metamaterial Antennas. Proceedings of UIST’25. https://hcie.csail.mit.edu/research/Meta_antenna/Meta-antenna.html
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