Combining lasers with plasma for better glass processing

Researchers from the Fraunhofer Institute for Surface Engineering and Thin Films (IST) in Germany have developed a technique to embed microstructures on glass more efficiently. The new approach involves combining a laser with a plasma beam, which initial results have demonstrated could make production processes more precise and economical.

Laser technology is a common approach used to insert microstructures into the tiny glass components found in devices such as mobile phones, cameras and electronics driver systems. However, laser processing can pose difficulties in such an application: if the laser’s energy density is too low, then insufficient radiation is absorbed in order to achieve the desired effect; if the power density is excessive, then undesired side effects, such as contamination by ablation debris, can occur.

In the technique developed at Fraunhofer IST, the team coupled atmospheric pressure plasma into the laser beam during the structuring process. ‘By using this laser-plasma hybrid technology, we have succeeded in conducting the structuring using far less energy,’ explained Professor Wolfgang Viöl, head of the Application Center for Plasma and Photonics at IST in Göttingen, Germany.

Plasma is a reactive gas that consists of free-moving, energy-rich electrons, ions and neutral particles. If the pressure in this gas mixture roughly corresponds to that of the surrounding environment, then this reflects atmospheric pressure or normal pressure plasma. Plasma is often used today in the machining of components to refine or to modify surfaces.

In order to combine the plasma with a laser, the Fraunhofer scientists designed a plasma source that initially delivers cold plasma, and secondly produces a very fine beam that can be coupled into the laser beam without any complications. ‘The effect of this plasma beam is that the laser radiation can be absorbed better, so that we can conduct the processing with relatively low laser energy,’ said Viöl.

Tests using the new approach with various glasses have been carried out, and Fraunhofer has recently submitted a patent application. In the future, applications for this technique could be vast, as microoptics made of glass are needed in telecommunications, as well as in consumer electronics or security technology. Tiny microstructures in glasses that are not visible to the naked eye could also be used as protection against plagiarism for high-grade optical components.

The next stage for the scientists is to extend their hybrid approach to other materials such as metals, ceramics or synthetics. The simultaneous use of laser and plasma could also make new processing or coating processes possible – even for temperature-sensitive materials such as textiles and paper.

A number of glass prototypes that were structured with the new procedure, as well as a plasma source which can be used for processing, will be exhibited at this year’s Optatec from May 20 to 22 in Frankfurt, Germany.

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