Dramatic advances in direct diode lasers

Abstract

Until now, diode laser concepts were used in applications in the multi-kilowatt range, in which actively cooled diode bars were used and combined via stacking. Per diode stack, laser outputs of just over a kilowatt can be achieved. If outputs of several kilowatts are to be achieved, the radiation of several stacks must be combined. A multi-kilowatt laser with industrially useful beam quality can only be realized through appropriate procedures such as wavelength or spatial combining. The beam quality of the coupled stacks corresponds to the quality of the individual stacks. If the beam quality of such systems is pushed to the limit of the feasible, this reduces the efficiency of the total system considerably. Today, such conventional fiber delivered diode lasers with a beam quality of about 100 mm*mrad achieve an outstanding efficiency of about 40%, but can only be used for laser soldering or other surface processing. With conventional diode lasers, if the beam quality is improved to about 40 mm*mrad, the efficiency falls to about 32%. In order to tap all the efficiency advantages of direct application of diode lasers and further improve the beam quality, TRUMPF has implemented a new concept in its direct diode lasers of the TruDiode series. The basis of this concept is the use of a fiber-coupled diode module with previously unachieved technical output characteristics. Another major advantage of the approach is that the diodes are passively cooled. This paper will highlight those characteristics, as well as provide technical details of the TruDiode series, extremely low running cost and associated application fields.