Scientists from Fraunhofer-Gesellschaft and Max-Planck-Gesellschaft are working together on a process for manufacturing prefabricated parts with hollow structural fibers with new geometries.
In the project "Laser-generated three-dimensional photonic elements" (LAR3S), their experience will be brought together to expand process knowledge and develop new technologies for the fabrication of various laser 3D structures. The Max Planck Institute for Light Science (MPL), the Fraunhofer Institute for Laser Technology ILT and the Fraunhofer Institute for Silicate Research ISC are involved.
The LAR3S project aims at a new approach to the production of laser 3D photonic components, focusing on selective laser-induced etching and reverse laser drilling. A key goal is to implement processes and procedures that can be automated.
For example, in order to process the inside of glass, laser radiation is used to penetrate the material so that a variety of transparent materials can be processed, with a wide range of geometric freedom in all three dimensions. The challenge is in the details - in order to achieve crack- and fracture-free results, researchers must have a detailed understanding of the material properties and processing.
Hollow glass fibers are typically achieved by stacking glass rods or tubes together and drawing them to a certain length, called the stack and draw process. In telecom applications, gas or vacuum hollow fibers that favor conventional cores can be used to achieve properties such as faster light speeds and reduced sensitivity to environmental changes.
When stack-and-draw methods are used, the structure of structured fibers is typically limited to hexagonal shapes. engineers at Fraunhofer ILT are continuing to develop a proprietary process - reverse laser beam drilling - using which it is possible to fully automate the manufacture of more complex, and therefore potentially more advantageous, structures. In this process, the laser beam is focused onto the back side through a transparent component and moved across the surface to be ablated using a scanner, effectively drilling backwards into the glass. This allows the introduction of almost any structure with a large aspect ratio into the fiber blank and is also possible with other transparent materials. In the future, these structures will be calculated by artificial intelligence on a computer and manufactured directly by laser.
The involvement of Fraunhofer ISC brings process control capabilities to the project: the removal of ablated residual material from the drilled holes. The project partners are optimizing the laser parameters and developing physical or chemical methods for process optimization. The goal is to create structures with customized dispersion properties in fiber preforms longer than 200 mm.
In addition, for selective laser-induced etching, focused ultrashort pulsed laser radiation is used to construct the volume and surface of the transparent material, making it crack-free and changing its chemistry so that it can be selectively etched later. As the focus is deflected in the workpiece, adjacent areas are modified and can be removed by wet chemical etching in a second process step. This two-part process also provides a high degree of geometric freedom for its users. The project partners want to optimize the process for the new geometry in laser microresonator fabrication. Such structures could be used in telecommunications and quantum technology.
The project is funded by the Fraunhofer Max Planck Collaboration and will run for three years.
