High-performance diode lasers are small, yet have a rosy future ahead of them. Here, inspection of the laser head of a fiber coupled design. Photo: Laserline
Thilo Horvatitsch

Pace Setter in the
Photonic Age

Diode lasers are now also conquering the factory work floors of automobile manufacturers. SCHOTT provides premium quality micro-lenses, important components for this key upcoming technology.

Diode lasers are always at work whenever a scanner at the cash register reads in the bar codes printed on milk or a shower gel package, a DVD is read, or exposure takes place inside a laser printer. Ever since efforts to generate light with a semiconductor chip succeeded for the first time ever in 1962, this technology has developed at an astonishing pace. Today, driven by its mass use in optical data transmission, these tiny sources of radiation make up more than half of the world’s laser market, valued at around six billion U.S. dollars per year. A special type of construction is now flexing its muscles on factory floors, as well: compact high-performance diode lasers are in the process of taking the front seats when it comes to industrial material processing. With output that can reach even the kilowatt range, they are proving themselves today in a wide range of applications, including welding of plastics and metals, hardening of surfaces, soldering of components or even fusion or torch cutting.

In the meantime, the German automotive industry, a rather influential clientele, has been relying more and more on powerful semiconductor lasers. ”We are seeing a real upswing in this direction,” confirms Volker Krause. The Managing Director of Laserline, a leading international manufacturer of diode lasers for use in industrial material processing, should know. This German company maintains business relations with nearly all well-known carmakers and has already installed more than 600 beam sources in the automotive industry, electrical engineering, plastics processing, medical technology and special equipment construction all over the world.

Laserline has primarily made a name for itself in the innovative field of direct use of diode lasers and offers beam sources with output ratings of up to ten kilowatts. ”This means braze joints between the roof and body of a car can be performed in the same way as attached parts, like doors or tailgates, with these types of lasers. Our customer Audi uses these throughout the entire company,” Krause notes. In global terms, the German automotive industry is regarded to be a pioneer when it comes to using this technology. In fact, the industry is gradually replacing lamp-pumped solid-state lasers with compact semiconductor lasers for direct use in manufacturing.

Here, one can say that high-performance diode lasers can be used as direct beam sources, on the one hand, and indirectly for ”pumping” (activating) the solid-state laser’s crystals, on the other. In the latter case, semiconductor lasers are superseding the flash and arc lamps as a pump source, as these require considerable maintenance. With this in mind, the difference between diode laser and conventional laser technology can also be easily explained. Here, diode laser light itself is not produced by pumping a crystal or creating a gas discharge inside a tube, as in a gas laser, but rather inside a miniscule microelectronic diode made of semiconductor material. One important advantage is that diode lasers convert electricity into light directly, without delay, and, thus, open the door to an entirely new age in laser technology, comparable to the leap in technology from the tube to the transistor.
Today, compact high-performance diode lasers achieve kilowatt outputs and even stand up to cutting during industrial processing of materials. Photo: Highyag-Laserline
Saving 100,000 euros in power

The benefits can be reaped in many areas: Diode lasers offer up to 10 times higher efficiency than conventional lasers, yet remain almost completely free of maintenance during a high life cycle of up to 30,000 operating hours. Most importantly, these are small and can be easily integrated into manufacturing technology. All in all, this represents a major advance over conventional laser installations. Rather than coming from an energy consuming cabinet the size of a human being, the same performance can be obtained from a unit the size of a shoe box. ”By comparison, a diode laser with 4 kW of output power that is in operation for 8,000 hours can easily save 100,000 euros per year on electricity costs,” Volker Krause estimates. As this suggests, an investment in this technology pays for itself rather quickly.

Ever since it became possible to control the beam quality more closely, a weakness in high-performance diode lasers, these advantages can be leveraged even more effectively. Divergent light is simply extremely difficult to focus and, therefore, needs to be optically processed in a complex manner, before it can be put to use in processing materials. Here, SCHOTT supplies an important component in FAC lenses for parallelizing the beam. Its reproduction characteristics need to be homogeneous, even in high volumes, but also capable of preserving the beam quality of the laser. ”There are only very few suppliers, like SCHOTT, for instance, that one can always depend on to deliver lenses that offer the necessary quality,” says Volker Krause.

If even the extremely demanding automotive manufacturers are satisfied with the ”entire package” they are receiving, it is safe to assume that this small laser has a bright future ahead of it, not only as an universal tool for use in industrial manufacturing, but also in interesting niches, such as laser surgery, industrial thermal drying or printing and display technology. In any case, Kraus notes that one development is already foreseeable: ”In five years, the diode laser will have replaced lamp-pumped lasers,” he says.