Germany Develops Direct Laser Welding Technology For Adhesive-free Fiber-to-chip Connections

Recently, researchers at the Fraunhofer Institute for Reliability and Microstructures (Fraunhofer IZM) in Germany and their partners have announced the successful development of a laser welding technique that efficiently secures optical fibers to photonic integrated circuits (PICs) without the need to utilize adhesives for bonding.
The technology was developed in response to biophotonic sensing technology and primarily utilizes miniaturized photonic integrated circuit (PIC) systems with highly stable fiber optic connections.

In the past, adhesives were often required for fiber optic interconnections of photonic integrated circuits. However, in the long run this solution leads to the occurrence of optical degradation phenomena and eventually optical transmission losses. The softness of the adhesive causes the position of the component to change over time and creates a point of interference between the two layers of glass. As the adhesive ages, this leads to signal degradation and brittle connections.
Due to the different volumes of the glass fibers and the substrate, the heat capacities of the two parts to be joined are unequal and therefore behave differently in terms of heating and cooling. Without proper compensation for the differences, this can lead to deformation and cracking during cooling. To solve this problem, the team used a separate tunable laser to uniformly preheat the substrate so that the melting phases of the fiber and the substrate occur simultaneously.
The technology developed in this project has gone beyond the experimental setup stage; the system they developed is designed for industrial environments. The Fraunhofer Institute for Reliability and Microstructure (Fraunhofer IZM) in Germany, in collaboration with Finicontec Service, implemented the technology process in an automated system and found the process to be highly reproducible and scalable. It is equipped with thermal process monitoring up to 1,300°C, a positioning system accurate to 1 μm, and imaging to identify the process and control software.
"The potential for high automation enables customers to use photonic integrated circuits (PICs) with maximum coupling efficiency. Industrial consolidation means a leap forward in biophotonics applications, but also in quantum communications and high-performance photonics." Gómez said.