Volker Krause is the founder and managing director of Laserline GmbH, which introduced the first direct diode laser to the market in 1997 and has, in the meantime, delivered 4,500 high power diode laser systems throughout the world. In this interview, he discusses the rapid developments in the power of diode lasers, the importance of research cooperation projects for technological development, and the potential of blue diode lasers.
Volker Krause: Thank you. Dr. Christoph Ullmann and I established Laserline GmbH in 1997 in the Koblenz Technology Center. We are still the managing partners and each of us owns half the company. When we established the company, we had a vision of getting diode lasers to a power level that is necessary for industrial joining processes. We have pursued and achieved this aim step by step. Laserline is now the leading manufacturer of diode lasers for industrial material machining—from welding, brazing, cladding and hardening to additive manufacturing and tape laying of carbon fiber tapes. This is also because, in addition to beam sources, we develop tailored optics for specific processes, which makes us unrivaled in many areas. We have grown organically and now have 320 employees, 270 of these in Germany. We have separate locations in China, the U.S., Japan, South Korea, and Brazil and a global sales and service organization.
Krause: We now offer a wide range of diode lasers up to the multi-kilowatt range with beam qualities of 4 to 200 mm mrad. In the year in which the company was established, we had powers of around 500 W. We achieved our goal of developing laser diodes at the level of lamp-pumped Nd:YAG lasers in 2009 with a 4-kW diode laser with 30 mm mrad. These days, 25 kW output power is feasible, even 60 kW on a prototype basis. And the potential is by no means exhausted. In the future, we will see diode lasers with more than 100 kW output power. However, the cooling technology is of key importance. It must be able to absorb and dissipate the waste heat around the semiconductor diodes. We have a patented solution for this and are pursuing a consistent modular approach. Basically, the multi-kW systems consist of modules each with more than 200 W power. That enables very compact systems, easily scalable, inexpensive systems.
Krause: That’s an important question. At present, the maximum electrical efficiency of a module is 70 percent; theoretically, with optimum cooling, 80 percent is possible. Therefore, logically the next target is to achieve efficiencies above 70 percent, which would correspond to almost three quarters optical power with just a quarter thermal output. The wall-plug efficiency of the overall systems currently reaches up to 50 percent. We assume that diode laser systems with up to 60 percent overall efficiency are feasible. The efficiency of semiconductor technology is unique.
Krause: The spectrum has developed continuously over the past 20 years. Diode laser technology has gone from strength to strength in the automotive industry since Audi first used diode lasers for brazing tailgates in 2002. It has also been used for aluminum welding in visible external areas since 2008. Our multi-spot solution for brazing hot-dipped galvanized sheets is a new process, which received the 2018 Innovation Award Laser Technology. These metal sheets are less expensive than electrogalvanized steel sheets, but are more difficult to work with. Our solution prepares the actual brazing area with two off-set front spots on the side—which more or less creates “guardrails” for the brazing process with the following main spot. This increases the quality and processing speed considerably. With innovative, efficient solutions, diode lasers have also become popular for cladding processes in the oil and gas industries. The same applies to plastics processing and heat treatment. No other heat source can be controlled within milliseconds as accurately as a diode laser. Additive processes, such as laser deposition welding and industrial 3D printing are also important new areas of application. Additive manufacturing offers enormous potential.
Krause: Blue diode lasers are a very important technology program for us. Development began with the EffiLas project funded by the German Federal Ministry of Education and Research (BMBF) together with OSRAM Opto Semiconductors, Dilas Diodenlaser and the Max Born Institute in Berlin. Our objective was to develop a blue high power laser to process very reflective non-ferrous metals like copper or gold. In 2018, we presented a first system with 700 W and a beam quality of 60mm mrad. The most important area of application is electric vehicles. A reliable bonding technology for highly conductive metals is needed – such as in battery production where copper foils just a few micrometers thick have to be welded or where copper has to be bonded to other metals. Non-ferrous metals absorb wavelengths in the blue range much better than infrared or green light. This allows much more accurate control of bonding processes, while the strong reflection in other wavelength ranges means that there is only a very narrow action window between not welding or cutting. The high absorption of the shortwave blue laser also alleviates the spatter problem. These benefits are also evident in additive manufacturing and in many other industries that use non-ferrous metals.
Krause: Collaboration with partners from science and industry—often within the scope of national and European funding initiatives—is very important for us. Contacts are established and expertise is transferred, with the result that ideas can be translated into marketable products much faster. In the BlauLAS project, the collaboration provided us with access to the necessary material for the 450-nanometer chips. In other projects, we established contacts in the oil and gas industries and the plastics industry. It’s important to develop visions with partners and to implement these together.
Krause: The development of diode laser technology is closely linked to Germany. Many leading competitors come here, which is also due to the pronounced special machine engineering expertise and effective government funding. Apart from that, U.S. and Chinese providers are our strongest competitors. The Chinese market is developing at an incredible rate, also because effective government funding is available there. Manufacturers and users of laser technology are developing dynamically. For Laserline, China is currently the most important sales market in which we still see outstanding perspectives and growth opportunities. As a system manufacturer in a complex, service and maintenance-intensive field of technology, we have an outstanding starting position. I look forward to our next 20 years with confidence.