DIODE LASERS
Coherent-Dilas offers 3-10kW direct beams, as well as 6kW and 8kW fibre-delivered units Coherent-Dilas’ technology is modular – it is
based on the same diode platform as that used to pump fibre lasers, ‘which is a very cost-sensitive market’, noted Biesenbach. Power can be increased with several modules to 1kW, which is ideal for sheet metal welding. Using several wavelengths with the same automated technology, Coherent-Dilas can offer up to 4kW with 25mm-mrad beam quality. ‘Application testing has shown that welds made with Coherent-Dilas’ direct diode laser systems are comparable with those made with a fibre laser,’ Biesenbach said. To reach higher brightness, Coherent-Dilas
uses T-Bar single emitters superimposed on a monolithic chip. Tis means optically more effort is put into the design, which increases the cost. Te company has achieved 8mm-mrad using the same platform as the 25mm-mrad T-Bar unit. ‘Tis is a nice result, but it is not yet a product,’ Biesenbach said. ‘We’ve developed this technology to be ready for the day – and the day will come in my eyes – when high brightness diode lasers will be used for tasks like cutting sheet metal. We are driving the T-Bar to the maximum in terms of brightness.’ A beam parameter product of 5mm-mrad can
also be achieved by halving the size of the T-Bar chips from the standard 100µm to 50µm. ‘Tat’s the beam quality of industrial multimode fibre lasers today,’ Biesenbach noted. However, since the diodes are only half the
width, they only have half the power. ‘You need double the number of chips to get to the same total power, compared to the standard 100µm wide emitter used as a pump source for fibre lasers.
12 LASER SYSTEMS EUROPE ISSUE 33 • WINTER 2016
Smaller and more numerous emitters will cost more to produce, which makes diode lasers more expensive than fibre lasers,’ Biesenbach added.
Speeding additive manufacturing ‘In the long run, diodes will be bright enough without needing an active material – fibre or disk – to achieve very high brightness, but we’re still a few years away from that,’ commented Kleine. Teradiode might disagree with that statement, but the high brightness diode laser is still a very young technology. Direct Photonics from Germany was another company developing high brightness direct diode lasers, but it has since been acquired by II-VI. Another potentially big
‘Direct diode lasers are definitely here for real;
market for diode lasers is for additive manufacturing, according to Biesenbach. ‘Today’s selective laser melting machines for 3D printing use precise fibre lasers to make very fine structures, but these machines are slow because of the single laser. If you combine a fine focus from a fibre laser and a rougher focus from a diode laser, the process can be engineered to run faster,’ he said. ‘[Diodes that are] small and inexpensive – and if
they have the right beam quality – would be a very interesting new market for diode lasers,’ Biesenbach added. Fraunhofer ILT is already working on this concept using diode lasers for SLM.
like Mazak, Panasonic and others adopting the technology… direct diode is the future of laser processing beyond fibre lasers
With companies
it’s the next big thing aſter fibre lasers,’ Pandey at Teradiode commented. Teradiode’s lasers are immune to back reflection. In addition, the beam combining process that forms the heart of the company’s technology produces an output beam with a wider spectral bandwidth, which can be controlled by design. ‘Using the broad wavelength range emitted by our direct diode systems gives a better absorption when cutting alloys [compared to cutting with the fibre laser wavelength],’ explained Pandey. ‘Tat’s an advantage for direct diodes that hasn’t been talked about as much, but is the reason direct diode lasers can cut faster and at higher quality, because these little composition changes in the alloy don’t all respond well to 1µm from a fibre laser. Fibre lasers get the job done, but a broader wavelength range hitting the material gives better absorption.
‘Reliability and other factors have to continue
to improve,’ Pandey continued, ‘but with companies like Mazak, Panasonic and others adopting the technology… direct diode is the future of laser processing beyond fibre lasers. Even big companies like Trumpf and others are very interested in this technology; it’s just that no one has really power scaled reliably to a point where it can be a contender to fibre lasers. We think we have done this.’
@lasersystemsmag |
www.lasersystemseurope.com
Coherent-Dilas
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