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So far, diode laser systems could not compete against CO2-lasers or DPSSL in industrial applications like marking or
cutting due to their lower brightness. Recent developments in high-brightness diode laser bars and beam forming
systems with micro-optics have led to new direct diode laser applications.
LIMO presents 400W output from a 200μm core fibre with an NA of 0.22 at one wavelength. This is achieved via the
combination of newly designed laser diode bars on passive heat sinks coupled with optimized micro-optical beam
shaping. The laser is water cooled with a housing size of 375mm x 265mm x 70mm.
The applications for such diode laser modules are mainly in direct marking, cutting and welding of metals and other
materials, but improved pumping of fibre lasers and amplifiers is also possible. The small spot size leads to extremely
high intensities and therefore high welding speeds in cw operation. For comparison: The M2 of the fibre output is 70,
which gives a comparable beam parameter product (22mm*mrad) to that of a CO2 laser with a M2 of 7 because of the
wavelength difference.
Many metals have a good absorption within the wavelength range of the laser diodes (NIR, 808nm to 980nm), which
permits the cutting of thin sheets of aluminium or steel with a 200W version of this laser. First welding tests show
reduced splatters and pores owing to the optimized process behaviour in cw operation with short wavelengths.
The availability of a top-hat profile proves itself to be advantageous compared to the traditional Gaussian beam profiles
of fibre, solid-state and gas lasers in that the laser energy is evenly distributed over the working area.
For the future, we can announce an increase of the output power up to 1200W out of a 200μm fibre (0.22 NA). This will
be achieved by further sophistication and optimisation of the coupling technique and the coupling of three wavelengths.
The beam parameter product will then remain at 22mm*mrad with a power density of 3.8 MW/cm2 if focussed to a
200µm spot. This leads to excellent laser cutting results with extremely small cutting kerfs down to 200μm and very
plane cutting edges. Process speeds rise up to more than 10m/min i.e. for thin sheets of stainless steel or titanium.
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