|
High Power Lasers have been used for years in corresponding applications. Constantly new areas and new processes
have been demonstrated, developed and transferred to fruitful use in industry. With the advent of diode pumped solid
state lasers in the multi-kW-power regime at beam qualities not far away from the diffraction limit, a new area of
applicability has opened. In welding applications speeds could be increased and systems could be developed with higher
efficiently leading also to new perspectives for increased productivity, e.g. in combined processing. Quality control is
increasingly demanded by the applying industries, however applications still are rare. Higher resolution of coaxial
process control systems in time and space combined with new strategies in signal processing could give rise to new
applications. The general approach described in this paper emphasizes the fact, that laser applications can be developed more
efficiently, more precisely and with higher quality, if the laser radiation is tailored properly to the corresponding
application. In applying laser sources, the parameter ranges applicable are by far wider and more flexible compared to
heat, mechanical or even electrical energy. The time frame ranges from several fs to continuous wave and this spans
approximately 15 orders of magnitude. Spacewise, the foci range from several µm to cm and the resulting intensities
suitable for materials processing span eight orders of magnitude from 103 to 1011 W/cm2. In addition to space (power,
intensity) and time (pulse) the wavelength can be chosen as a further parameter of optimization. As a consequence, the
resulting new applications are vast and can be utilized in almost every market segment of our global economy (Fig. 1).
In the past and only partly today, however, this flexibility of laser technology is not exploited in full in materials
processing, basically because in the high power regime the lasers with tailored beam properties are not available and
consequently many applications are not developed yet or are not operatable at optimized parameters.
Because of their systematic flexibility in the sense layed out above, solid state lasers are the class to be considered in this
context, diode pumped solid state lasers as well as high power diode lasers. In the past years the intrinsic beam quality of
diode lasers in terms of divergence, smile and stability as well as the lifetime increased significantly. Single bars with
beam parameter products around BPP=20 mm*mrad have been demonstrated. Lifetimes of 30.000h (90%) @100W cw
operation are available /29/, /30/. Consequently the market increasingly accepts this type of lasers and new application
domains like welding and metal deposition are investigated.
Also the beam quality of high power diode lasers has been increased at many groups working in the field of coherent
coupling or incoherent superposition [1]. Corresponding by the direct application of high power high quality diode lasers
increasingly enters the markets. For all concepts the key demand is its applicability in terms of the specification of the process the laser is designed for.
The characteristics of the laser with respect to power and energy on the one hand and quality in terms of space (spacial
coherence, focussability), time (puls e duration and duty cycle) and wavelength have to match the demands of the specific
application. Therefore, we face an intense trend for diversification of lasers in the named characteristics. There may be
dominant large markets and niches but on the other hand there will not be a "best" laser or laser concept in the general
sense.
|
