Researchers in Germany have developed a technique for automated direct welding of photonic integrated circuits (PICs).
Fibre interconnection strategies for PICs and other photonic devices and optical fibres usually involved adhesives, but these can degrade over time and lead to high optical transmission losses.
As part of the PICWeld Eurostars project, researchers at Fraunhofer IZM in Germany worked with LioniX International, Phix Photonics Assembly and ficonTEC Service to develop a robust laser welding process for fixing optical fibres to PICs. Integrating the process into an automated alignment system is essential for cost effective assembly of fibres and photonics chips.
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The research team led by Dr. Alethea Vanessa Zamora Gómez used a CO2 laser to create direct, thermally robust and transparent glass-glass joint for the first time.
“With our CO2 laser welding system, we have expanded the process behind the existing principle: The high automation potential in particular allows customers to use PICs with maximum coupling efficiency. Industrial integration means a leap forward for the areas in which biophotonics can be applied, but also for quantum communication and high-performance photonics,” said Gómez.
The system is equipped with thermal process monitoring up to 1300 °C and a positioning system accurate to 1 µm, image recognition processes and control software for automated welding of glass-to-glass joints, including collimators, PICs, integrated waveguides and multi-lens arrays.
The project evaluated the performance of the welding system, tackling a number of technological challenges. As the glass fibres and the substrates have different volumes, the heat capacities of the two parts to be joined are also unequal. This discrepancy results in very different heating and cooling behaviour, which can lead, for example, to deformation and cracks during cooling. The solution of the photonics experts was to preheat the substrate evenly by means of a separate, individually adjustable laser, so that the melting phase of the fibre and the substrate is achieved simultaneously.