Lithium Tantalate Modulator Achieves 400 GBit/s With Copper Electrodes

Optical Data Transmission Lithium Tantalate Modulator Achieves 400 GBit/s With Copper Electrodes

2026-03-23 From Hendrik Härter | Translated by AI 2 min Reading Time

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Researchers have developed a new type of component to transmit data quickly and reliably. The electro-optical modulator transmits data through fiber optic cables and can be produced in large quantities at low cost.

The compact modulator enables fast and energy-efficient data transmission and can be manufactured cost-effectively.(Image: Hugo Larocque, EPFL) — The compact modulator enables fast and energy-efficient data transmission and can be manufactured cost-effectively.
(Image: Hugo Larocque, EPFL)

The lithium tantalate modulator developed at the Karlsruhe Institute of Technology (KIT) in collaboration with EPFL is based on lithium tantalate (LiTaO₃) as an electro-optical material. However, the breakthrough is not in the material itself, but in the manufacturing process: For the first time, the researchers are integrating lithium tantalate with standard copper metallization from CMOS production.

"The decisive progress lies in the copper electrodes and in the way we manufacture them," explains Professor Christian Koos from the Institute of Photonics and Quantum Electronics (IPQ) at KIT. Copper offers two advantages over the previously used gold electrodes: better conductivity with lower losses and an almost mirror-smooth surface after chemical-mechanical polishing (CMP). This smooth surface considerably simplifies hybrid integration with electronic chips.

400 GBit/s Without Readjustment

In tests, the modulator achieved stable data rates of over 400 GBit/s without the drift and associated calibration effort that is common with many optical systems. "The modulator runs stably without us having to keep correcting the settings," confirms Alexander Kotz from IPQ. This long-term stability is crucial for use in data centers, where thousands of such components work in parallel.

The data rate of 400 GBit/s achieved is not yet the maximum. "We are working at the limit of what is technically possible today. With more powerful driver electronics, we could increase the data rates even further," says Kotz. Currently, the available driver electronics limit the bandwidth, not the modulator itself.

Scalable Production for AI Infrastructure

The real advantage for the industry lies in the manufacturability: the modulators are created using the same processes that are already used millions of times in chip production. This enables cost-effective mass production, which is a critical factor in view of the exponentially growing bandwidth requirements in AI clusters and hyperscale data centers.

The technology thus directly addresses the bottleneck of modern AI systems: the exchange of data between GPUs and storage systems. While the computing power of individual chips continues to increase, networking is becoming the limiting factor. Optical connections with high bandwidth and low energy consumption are the only scalable solution here. (heh)

Link: Heterogeneously integrated lithium tantalate-on-silicon nitride modulators for high-speed communications. Nature Communications. Retrieved March 18, 2026

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