Beam Addition of Nd: YAG-High-Power-Lasers

摘要

In order to increase the laser power for material processing, especially for welding applications, different set-ups for beam addition are used. The most wide used method is to overlay the beams of two or more independent lasers directly onto the workpiece Welding results of aluminium alloys with two lasers in the 2 kW class are shown. The disadvantage of the large welding optics by using this method could be reduced if the laser beams are coupled into one optical fiber. Results of experiments with three identical cw Nd:YAG lasers with 150 W average power and a beam parameter product of 17 mm mrad each are shown. Three different schemes for coupling these laser beams into one optical fiber are presented. One is to overlay the laser beams at the core of the fiber. Another scheme is to couple the laser beams into fibers and image the endfaces of these fibers onto one fiber endface. The last coupling scheme is to bundle the fibers and place them endface to endface in front of a thicker fiber. Losses and the beam parameter product behind the final fiber are compared. Also an oscillator-fiber-amplifier system is introduced. This yields a very simple system to increase the laser power under keeping of the beam quality