Laser system maker Trumpf has developed a femtosecond laser to weld glass light guides used in its own laser machines.
Trumpf is currently building the laser welding system to mass produce glass protective caps for the laser light cables in its production plant in Schramberg, Germany. The caps would traditionally be glued to the cables. Using a femtosecond laser to weld the components reduces costs and increases the durability of the seam.
Elke Kaiser, applications engineer at Trumpf, commented: ‘The laser system also serves as a pilot system to demonstrate to potential users that new, innovative laser methods are reliable and ready for deployment in glass processing and offer immense advantages.’
The new laser welding methods also mean that optical beam paths are no longer contaminated with glue, and there is no evaporation and no long-term embrittlement of adhesives.
Glass is hard and brittle, has lower thermal conductivity than metal, and tends to crack when heated unevenly due to the internal tension developed. Femtosecond laser systems can prevent such cracking. ‘The laser system must permit variable programming of pauses and pulses,’ explained Kaiser.
Glass is permeable to light with wavelengths ranging from ultraviolet to near infrared. Absorption takes place only when the energy densities are very high, so that processing within the glass is facilitated.
The highest performance density lies deep in the lower glass at the focal point. The energy from several thousand laser beam pulses causes a melt pool to be created and pushed upwards in just a few milliseconds. Skillful thermal management and an optimal ratio of pulses and pauses prevent the glass from cracking.
The joint strength of the glass parts depends primarily on the level of pulse energy. The pulse energy for 1,030nm infrared light needs to be 9µJ.