The vision behind it is as pragmatic as it is ambitious. Instead of putting optical chips into operation with complex experimental adjustments, the coupling of optical fibre and chip is to be standardized, reproducible and automatable. The new connection concept was developed under the leadership of Prof. Dr. Wolfram Pernice at the Kirchhoff Institute for Physics. It could form the basis for faster and more cost-effective production of photonic integrated systems - and thus for technologies that play a central role in data centers, communication networks or future quantum architectures.

Photonic integrated circuits (PICs) use light instead of electrons to transmit information. They offer extremely high bandwidths, minimal delay times and are also considered more energy-efficient than conventional electronic systems. All optical components, such as waveguides, are integrated directly on the chip. Bulky arrangements of mirrors and lenses are replaced by compact structures. Their innovation potential ranges from quantum communication to neuromorphic computing and high-speed optical communication.

However, the technological hurdle is particularly evident at a crucial point: when coupling the data in and out. Optical fibers are generally used to ensure that the light reaches the chip with minimal loss. These must be positioned with an accuracy of less than five micrometers in all spatial directions - otherwise a large proportion of the signals will be lost. Until now, this adjustment has been carried out using so-called active alignment. In this process, the optical fibers are precisely aligned for maximum light transmission during operation and then fixed in place. According to the Heidelberg researchers, however, this process is slow, cost-intensive and difficult to automate.

An alternative solution to date has been to integrate microlenses on fibers and chips in order to increase the alignment tolerances. However, this method also has its limits. The production of such lenses is complex and only works for a narrow wavelength range - a disadvantage that limits the high bandwidth of photonics as a key advantage.

The team from Heidelberg is therefore taking a different approach: a novel connection concept that mechanically standardizes the coupling between fibre and chip. Fibre optic cables are precisely arranged in a glass block and provided with standardized alignment holes. The counterpart is created directly on the chip surface - manufactured using high-precision 3D microprinting. This element acts like a "connector".

The actual coupling takes place via three-dimensionally printed total reflection couplers. They redirect the light waves with low loss and are designed as super broadband components for the wavelengths between 1,500 and 1,600 nanometers that are typical in telecommunications. They guarantee practically constant transmission in this range. "Thanks to this innovative plug-in solution, we guarantee that no data is lost during the coupling process," explains Erik Jung, a doctoral student in Prof. Pernice's research group.

With the new concept, the researchers also succeeded in efficiently controlling a neuromorphic photonic processor with 17 ports - i.e. 17 communication endpoints. This demonstrates the practical feasibility of the approach.

"Our approach shows how broadband, low-loss and scalable connections for light-controlled microchips can be easily realized. This 'connector' paves the way for automated, reproducible and efficient mass production of photonic integrated systems," says Wolfram Pernice.

According to Erik Jung, the connection concept is compatible with hybrid systems in which electronics and photonics are combined. At the same time, modular and flexibly reconfigurable architectures are supported. The "connector" could therefore become a central component for next-generation computing and communication systems - for example in optical sensor technology.

The work was carried out together with researchers from the Institute for Molecular Systems Engineering and Advanced Materials at Heidelberg University. They are embedded in the Cluster of Excellence "3D Matter Made to Order". The results were published in the journal Science Advances.

Original publication:
Jung, E., Gehring, H., Brückerhoff-Plückelmann, F., Krämer, L., Vazquez-Martel, C., Blasco, E., & Pernice, W. (2025, September 26). Ultrabroadband plug-and-play photonic tensor core packaging with sub-dB loss. Science Advances. DOI:10.1126/sciadv.adz1883