17 Jun Fiber-PIC connections for quantum technologies
Researchers at the Fraunhofer Institute for Reliability and Microintegration IZM have developed an adhesive-free laser welding process for coupling photonic integrated circuits (PICs) with optical fibers. The coupling should also be usable in cryogenic environments of up to four Kelvin, i.e. -269.15 °C.
As part of the QWeld research project, the researchers developed the laser welding process for vertical, optical connections using the PICWeld process system prototype, which had already been built and installed in a previous research project. According to the researchers, the system was the first time ever that a direct edge connection between a glass fiber and a PIC made of quartz glass could be created using laser welding. The longevity and thermal robustness should offer a clear advantage over the conventional bonding method using adhesives.
Adaptations to high process requirements
According to the researchers, a special feature is the vertical coupling of the fiber with the PIC, which usually takes place at a specific angle of attack. During welding, the laser hits the contact point between the PIC and the glass fiber on both sides and creates the material bond within a few seconds. This manufacturing process should therefore save a great deal of time. The changed boundary conditions, in particular the SiO2-SiO2 material pairing and high precision requirements for alignment with each other, have necessitated far-reaching further development of the process and the associated system. According to the researchers, local preheating, extended alignment options and measurement technology were integrated. The welded joint is durable, reproducible and can be automated, for example for the series production of PICs.
Project coordinator and scientist from Fraunhofer IZM Dr. Alethea Vanessa Zamora Gómez summarizes: “In the newly developed laser welding process, a certain area of the SiO2 layer of the PIC is preheated with a CO2 laser to minimize the temperature difference between fiber and PIC during welding. This preheating process promises to solve all current challenges of fiber bonding for PICs at cryogenic temperatures. Thanks to the use of CO2 lasers, the automated process is cheap and reliable to manufacture, making it attractive for application in industry.” In addition, the researchers believe that further applications are possible in biophotonics, sensor technology and high-power lasers.
Project funding
The QWeld project was funded by the ‘Scientific preliminary projects (WiVoPro): Photonics and Quantum Technologies’, funded 100% by the Federal Ministry of Education and Research (BMBF). The QWeld project ran from 01.08.2022 to 31.12.2024 as part of the ‘Quantum Technologies – from Fundamentals to Market’ program. The project was coordinated by Dr. Alethea Vanessa Zamora Gómez from Fraunhofer IZM.
Source and image: www.izm.fraunhofer.de