09 Mar A plug connector for PICs
One of the biggest technical challenges of photonic integrated circuits (PICs) lies in coupling data into and out of the chip. To transfer light onto the chip with minimal losses, optical fibers are commonly used. These fibers must be positioned with an accuracy of less than five micrometers in all spatial directions, otherwise a large fraction of the light is lost.
Until now, this alignment has typically been performed using active alignment. In this process, the glass fibers are precisely adjusted during operation to achieve maximum light transmission and are then fixed in place. However, this process is slow, expensive, and difficult to automate.
An alternative approach involves integrating tiny microlenses on the fibers and chips to increase alignment tolerances. However, manufacturing these lenses is very complex and works only within a very narrow wavelength range, which compromises the high data-rate bandwidth – one of photonics’ main advantages.
Glass block and 3D microprinting
Researchers at the University of Heidelberg have now reported a novel concept for connecting fiber and chip. Under the leadership of Prof. Dr. Wolfram Pernice at the Kirchhoff Institute for Physics, the team uses fiber-optic cables arranged precisely within a glass block and equipped with standardized alignment holes.
According to the researchers, the corresponding counterpart required for coupling – functioning like a plug connector – is produced directly on the surface of the photonic microchip using high-precision 3D microprinting.
Coupling between the optical fiber and the photonic chip is achieved via three-dimensionally printed total internal reflection couplers, which redirect the light waves with very low losses. These ultra-broadband couplers are designed for the telecommunications wavelength range between 1500 and 1600 nm.
“With this innovative plug-in solution, we ensure that no data are lost during the coupling process,” said Erik Jung, a doctoral researcher in the group.
Using this new connection concept, the researchers report that they were able to efficiently address a neuromorphic photonic processor with 17 ports, meaning communication transmission points.
A step toward mass production
“With this connector, the path is clear for automated, reproducible, and efficient mass production of photonic integrated systems,” said Pernice. According to Jung, the connection concept is also compatible with hybrid electronic-photonic systems, while simultaneously supporting modular and flexibly reconfigurable architectures. The connector concept could therefore become a key building block for next-generation computing and communication systems, as well as future applications – for example in optical sensing technology.
The work was carried out jointly with researchers from the Institute for Molecular Systems Engineering and Advanced Materials at Heidelberg University. It was part of the ‘3D Matter Made to Order’ Cluster of Excellence.
Original publication:
[E. Jung, H. Gehring, F. Brückerhoff-Plückelmann, L, Krämer, C. Vazquez-Martel, E. Blasco and W. Pernice: Ultrabroadband plug-and-play photonic tensor core packaging with sub-dB loss. Science Advances, 26. September 2025, DOI: 10.1126/sciadv.adz1883]
Source: www.uni-heidelberg.de
Image: Erik Jung