Micro hair for optical-tactile sensor device casted from a laser generated tool.
Practical optics was the main passion of Josef von Fraunhofer, the 19th century German optician who invented the diffraction grating, made optical glass and discovered dark absorption lines in the spectrum. It’s a vision that the Fraunhofer Society is devoted to as well. This is in great contrast to many institutions that are devoted solely to foundational research. The Society generates two-thirds of its financial volume by carrying out orders from the industry and with state-financed research projects. A third is contributed by the German Federation and States as basic financing, so that the industry can work out solutions to problems that will become relevant to society in 5-10 years.
The Society was founded in Munich in March of 1949 by representatives of industry and academia, the government of Bavaria and the burgeoning Federal Republic of Germany. Today, with more than 80 research institutes and more than 17,000 employees, the Fraunhofer Society continues to push innovation forward. In 2009, it had total finances of 1.5 billion euros at its disposal for applied research.
A win-win for research and industry
We believe our greatest capital is our well-educated personnel. We place great emphasis on education, and all of the Fraunhofer Institutes work closely with universities. The leader of one of the institutes holds a chair at a cooperating university. In this way, we allow students to easily transfer from the university to an institute to conduct applied research. They can conduct their final thesis at Fraunhofer and obtain an academic degree through the cooperating university.
Students are integrated into industrial projects throughout their studies. We encourage them to make professional contacts very early on. Once they finish, graduates can supplement the specialized expertise they obtain with methodical competence; some even go on to found their own companies. These spin-offs are often located near a Fraunhofer Institute. In this way, our know-how makes it to places where it can be implemented profitably.
The mutual transfer of knowledge between the Fraunhofer Society and industry benefits both: Companies receive tailor-made solutions for their individual questions, within the scope of contract research, and the Society, reciprocally, has access to the latest technological topics in the industry. In total, the entire German economy profits from this transfer of technology.
Laser expertise in Aachen
In Aachen—a center for technological innovation—the Fraunhofer Society is represented by three institutes, one of which is the Fraunhofer Institute for Laser Technology (ILT). With around 300 employees and more than 11,000 m2 of usable floor space, it is among the world’s most important contract research and development institutes for laser development and applications. On average, the Fraunhofer ILT files one patent each month. Its core expertise is in developing new laser radiation sources and components, laser measuring and testing technology as well as laser manufacturing.
Overall, we are engaged in laser plant engineering, process control and regulation, modeling as well as system engineering. The services range from feasibility studies to process qualification to customer-tailored integration of laser processes in a production line.
We maintain close contact with industrial partners. For example, we offer our long-term partners the chance to locate in our application center as guest companies and to use our technical infrastructure. There they can implement their ideas in their own separate laboratories. Our research emphasis is on the development of radiation sources and creating new applications. The following are some recent examples of our work.
The 400-W femtosecond laser
Femtosecond (fs) lasers are key to ultra-precise processing. Unlike longer nanosecond pulses or continuous wave lasers, with fs lasers there is no direct interaction between the light and the dispersing material. This enables an extremely precise amount of material to be ablated. Up until now, however, the use of these lasers has been limited by their relatively low median output power. Researchers at the Fraunhofer ILT have now developed an ultra-short pulsed laser with pulse durations of less than a picosecond.
These pulses—which are less than a quadrillionth of a second—allow the material to evaporate before it becomes too warm and deforms. With a median output of more than 400 W, this new radiation source achieves an output power eight times higher than commercial femtosecond lasers. By simplifying fs laser systems and the costs bound up with them, we have created an essential prerequisite to their extensive application in the industrial environment. In medical technology, electronics, solar technology and the aerospace industry, the innovative radiation source can be used to ablate, drill and structure surfaces. We are working on scaling the laser to outputs greater than 1,000 W.
Higher efficiency in photovoltaics
In the middle of the next decade, the cost of solar electricity will likely even out with the price of conventionally produced electricity in Germany. In order for this to happen, however, the production costs of solar cells must fall, their efficiency must improve, and the throughput rate production must increase. These are the goals of the 6 million euro research and development project called the Next Generation Solar Cell and Module Laser Processing Systems (SOLASYS) supported by the European Union. Led by the Fraunhofer ILT, ten companies are working out the economic feasibility of laser applications in the photovoltaic sector.
Currently lasers are only used sporadically to manufacture solar cells. Now, researchers have shown that, using laser drilling, SOLASYS can reduce production costs for silicon solar cells. In the “metal-wrap-through” concept, the metallic contacts of the front side of the cell are guided through drill holes with a diameter of a human hair to the rear side of the cell. It is necessary to produce up to 100 drill holes in less than a second.
To reach these goals, we rely on the 400-W fs laser to process the silicon cells. We have developed a contact-free procedure that can drill more than 3,000 holes per second at a diameter of 40 µm in silicon cells. This procedure enables new cell designs and, thus, higher efficiency. With new optical systems and improved radiation concepts, we are aiming to reach drilling speeds of up to 10,000 drill holes per second.
Guided cell growth
Our employees are very active in biotechnology and medical technology. Amongother things, we are working on possible applications for laser processes to produce medical-technical products. With brilliant fiber lasers, we join plastic medical products such as catheters and microfluidics under sterile conditions without influencing their functionality. In the field of surface functionalization, our researchers have developed procedures to favor the guided development of biological cells into tissue.
The Fraunhofer Society works closely with international partners. Our institute cooperates, for example, with the University of Michigan and the University of Central Florida in the United States. We are also represented by the Center for Laser Technology CLP in Plymouth, Michigan, U.S.A., and we are a member of the Laser Institute of America. Since 1979, we have participated in the Coopération Laser Franco-Allemande in Paris with leading French research facilities.
We hope that the Fraunhofer Society’s innovative projects and applied focus would make our namesake proud.
Reinhart Poprawe is the director of the Fraunhofer Institute for Laser Technology and Chair of Laser Technology at the RWTH Aachen University in Germany.