Enabling terahertz communication: High-frequency signal conversion; amplifier-multiplier; electromagnetic wave absorber.
Researchers from ETH Zurich developed a plasmonic modulator capable of converting electrical signals into optical signals with a frequency of over a terahertz.
The modulator is a tiny nanostructure made up of various materials, including gold, and makes use of the interaction between light and free electrons within the gold. It converts signals directly, reducing energy consumption and increasing measurement accuracy. It can also be used with any frequency from 10 megahertz to 1.14 terahertz, reducing the number of components needed for different frequency ranges.
ETH spin-off company Polariton Technologies is working to bring the modulator to market. Applications include high-performance measurement technology as well as optical fiber cables that connect 6G base stations and data centers. [1]
Researchers at Massachusetts Institute of Technology (MIT) developed a terahertz amplifier-multiplier system that enables the generation of high-power terahertz waves on a chip without bulky silicon lenses.
“To take full advantage of a terahertz wave source, we need it to be scalable. A terahertz array might have hundreds of chips, and there is no place to put silicon lenses because the chips are combined with such high density. We need a different package, and here we’ve demonstrated a promising approach that can be used for scalable, low-cost terahertz arrays,” said Jinchen Wang, a graduate student in the Department of Electrical Engineering and Computer Science at MIT, in a statement.
The device uses a thin, patterned sheet of material affixed to the back of the chip. The sheet has a dielectric constant between silicon and air, which minimizes the amount of signal that is reflected at the boundary and means most waves will be transmitted out the back rather than being reflected. The chip itself uses transistors developed by Intel that have a higher maximum frequency and breakdown voltage than traditional CMOS transistors.
The chip, which could be used in terahertz arrays for applications such as security scanners or air pollution monitors, generated terahertz signals with a peak radiation power of 11.1 decibel-milliwatts. It can also be fabricated at scale. The researchers plan to demonstrate this scalability by fabricating a phased array of CMOS terahertz sources. [2]
Researchers from the University of Tokyo and Nippon Denko Co. created an electromagnetic wave absorber for waves between 0.1 and 1 terahertz. When placed on the covers of transmitters and antennas, the absorber can inhibit the transmission or reflection of electromagnetic waves, enhancing communication precision.
The absorber is composed of an electrically conductive metal oxide called lambda-trititanium-pentoxide (λ-Ti3O5), insulated within a titanium dioxide (TiO2) coating. It is made in powder form, which can be turned into a 48-micron thin film through compression molding and then applied to surfaces as needed. It is resistant to heat, water, light, and organic solvents.
“Our strategy was to combine an electrically conductive material with an insulating material. When a terahertz wave passes through, its alternating electric field induces scattering of the electric current generated inside of the conductive material, which causes energy loss and results in the dissipation of electromagnetic energy,” said Shin-ichi Ohkoshi, a professor from the Graduate School of Science at the University of Tokyo. “This dissipation of interfering waves enables the suppression of noise, i.e., unwanted waves, resulting in a clear signal.” [3]
[1] Horst, Y., Moor, D., Chelladurai, D. et al. Ultra-Wideband MHz to THz Plasmonic EO Modulator. Optica 2025, 12: 325. https://doi.org/10.1364/OPTICA.544016
[2] Wang, J., Sheen, D., Chen, X., et al. A 232-260GHz CMOS Amplifier-Multiplier Chain with a Low-Cost, Matching-Sheet-Assisted Radiation Package and 11.1dBm Total Radiated Power. IEEE Intl. Solid-State Circuit Conf. (ISSCC), San Francisco, CA, Feb. 2025. https://ieeexplore.ieee.org/document/10904783
[3] Ohkoshi, S., Tsuzuo, Y., Yoshikiyo, M., et al. Ultrathin Terahertz-Wave Absorber Based on Inorganic Materials for 6G Wireless Communications. ACS Applied Materials and Interfaces, January 31, 2025. http://dx.doi.org/10.1021/acsami.4c17606
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