High Power comes to one’s finger tip

08 January, 2025

Watt level output power demonstrated from a silicon photonics device that can help to replace benchtop systems from the future technologies with mass deployability.

A recent development at DESY has led to the realization of a millimeter-scale optical amplifier that delivers more than one watt of output power directly on a silicon-based photonic microchip. This marks a substantial advancement in integrated photonics, where compact systems have traditionally been limited by low power output. The new amplifier offers an effective solution to this limitation and could replace large external amplifiers in a wide range of applications—from medical and industrial laser systems to telecommunications and future accelerator technologies.
The key to this breakthrough lies in the use of a Large Mode Area (LMA) waveguide structure. By guiding the optical mode from a narrow silicon nitride waveguide into a thulium-doped aluminum oxide cladding, the design enables the light mode to expand into a broader cross-sectional area. This “floating” mode interacts with a large number of excited ions, allowing for efficient energy extraction during signal amplification. The LMA geometry thus overcomes the traditional trade-off between chip size and optical power.
Moreover, the amplifier employs a clever chip layout that routes the signal through the gain region multiple times via 180-degree turns, enhancing the amplification without expanding the device footprint. The entire active area measures only four square millimeters, yet it supports high gain and preserves signal quality, making it suitable for integration in complex photonic circuits.
This approach demonstrates that high-power, chip-scale optical amplifiers are not only feasible, but can also be implemented using scalable fabrication methods. Such integrated systems pave the way for new generations of compact, reliable, and cost-effective devices across various scientific and industrial domains.
This work was carried out at DESY within the Ultrafast Optics and X-ray (UFOX) group, under the leadership of Franz Kärtner. The project team was led by Neetesh Singh, who conceived and designed the LMA amplifier and coordinated fabrication, and experimental validation of the amplifier system.
This work was funded both by the European Innovation Council - EIC-Pathfinder Program “Femtochip” and by the Priority Program 2111 of the German Research Foundation (DFG): “Ultra-fast signal processing using nanophotonic/electronic technology” Project PACE (403188360). The extensive fabrication was carried out in cooperation with the company LIGENTEC, SA in Switzerland and the group of Sonia M. Garcia-Blanco at the MESA+ Institute of the University of Twente in the Netherlands, see also https://www.femtochip.eu/.
The results have been published in Nature Photonics and reflect ongoing efforts to merge high-performance laser technologies with integrated photonics.

Reference
Originaler Artikel auf desy.de (EN): www.desy.de
Original Article on desy.de (DE): www.desy.de

Watt-class silicon photonics-based optical high-power amplifier, N. Singh, J. Lorenzen, K. Wang, M. Gaafar, M. Sinobad, H. Francis, M. Edelmann, M. Geiselmann, T. Herr and F. X. Kärtner, Nature Photonics (2025).
DOI: 10.1038/s41377-024-01681-1-y