Researchers at IBM Research Europe and EPFL have created a traveling-wave parametric amplifier (TWPA) based on photonic chips that enable ultra-broadband signal amplification in a previously unheard-of tiny size. The study was published in Nature.
A focus-stacked macro photograph of a fabricated gallium phosphide photonic chip featuring multiple spiral waveguides and other test structures. The chip width is just 0.55 cm across. Due to the high Kerr nonlinearity of gallium phosphide, its high refractive index, and its negligible two-photon absorption, extremely efficient optical parametric amplification and frequency conversion over S, C, and L optical communication bands are achieved using this chip. Image Credit: Nikolai Kuznetsov (EPFL).
In modern communication networks, optical signals transfer large volumes of data. However, these optical signals must be amplified to travel vast distances without losing information, much like a weak radio transmission.
For many years, erbium-doped fiber amplifiers (EDFAs), the most widely used amplifiers, have fulfilled this function by allowing for longer transmission lengths without requiring frequent signal regeneration. Erbium-doped fiber amplifiers (EDFAs) have a narrow spectral bandwidth, which limits the growth of optical networks.
Researchers have been looking for methods to create more potent, adaptable, and small amplifiers to satisfy the increasing need for high-speed data transfer. Even while AI accelerators, data centers, and high-performance computing systems manage ever-increasing amounts of data, the limitations of conventional optical amplifiers are becoming increasingly clear.
There is a greater need than ever for ultra-broadband amplification or amplifiers that operate across a wider range of wavelengths. Although they provide some improvement, current solutions—like Raman amplifiers—remain excessively complicated and energy-intensive.
The researchers were led by Paul Seidler at IBM Research Europe – Zurich and Tobias Kippenberg at EPFL.
The new amplifier, which uses gallium phosphide-on-silicon dioxide technology, achieves a net gain of more than 10 dB over a bandwidth of about 140 nm, three times broader than a typical C-band EDFA.
Unlike traditional amplifiers that rely on rare-earth elements, this new amplifier leverages optical nonlinearity, where light amplifies itself through interaction with a material.
By precisely engineering a miniature spiral waveguide, researchers created an environment where light waves reinforce each other, boosting weak signals while minimizing noise. This technique enhances efficiency and allows for operation across a significantly broader range of wavelengths within a compact, chip-sized device.
The team selected gallium phosphide due to its remarkable optical characteristics. First, light waves can interact with it to increase the strength of the signal because of its great optical nonlinearity. Second, light can be closely contained within the waveguide because of its high refractive index, resulting in more effective amplification.
The scientists considerably reduced the amplifier's footprint. They made it feasible for next-generation optical communication systems by employing gallium phosphide to produce excellent gain with a waveguide that was just a few cm long.
The researchers showed that their chip-based amplifier could maintain low noise levels while achieving a maximum gain of 35 dB. Additionally, the amplifier could handle input powers ranging over six orders of magnitude, allowing it to amplify exceptionally faint signals. Due to these characteristics, the new amplifier can be used for various purposes outside of telecommunications, like precision sensing.
The amplifier significantly improved the performance of coherent communication signals and optical frequency combs, two essential technologies in contemporary photonics and optical networks. This demonstrates that photonic integrated circuits can outperform conventional fiber-based amplification devices.
The new amplifier will significantly impact future data centers, AI processors, and high-performance computing systems—all of which stand to gain from quicker, more effective data transfer. Furthermore, the uses go beyond data transfer, including metrology, optical sensing, and even LiDAR systems for self-driving cars.
Journal Reference:
Kuznetsov, N., et al. (2025) An ultra-broadband photonic-chip-based parametric amplifier. Nature. doi.org/10.1038/s41586-025-08666-z