Since 2000, every two years scientists and developers who take new paths in terms of applications for laser light are acknowledged and supported with the Innovation Prize awarded by the Berthold Leibinger Foundation. This year on September 15, 2008 four prizes worth 40,000 euros were awarded in the area of ultrashort impulse laser technology, excimer lasers, new laser sensors and silicon photonics. 

The research group of Robert Bosch GmbH and its subsidiary Bosch Rexroth AG comprising Jens König, Thorsten Bauer, Markus Willert and Ulrich Graf won the 1st prize, worth 20,000 euros for their work on "ultrashort impulse laser technology – the future of high precision micro-milling on a large scale", beating 32 other applications from universities, institutions and industry. By awarding the prize the jury of renowned experts acknowledged the implementation of scientific fundamentals in the application of ultrashort impulse laser technology in industrial serial production. Ultrashort impulse technology will revolutionize micro-milling.

With short laser impulses it is possible to incorporate structures in the micrometer range into almost every material very quickly and with a high degree of precision. As one of the first applications at Bosch the new technology is being used in the production of sensors and diesel fuel injection systems. The basic work was funded by the German Federal Ministry of Education and Research in the joint projects PRIMUS and PROMTUS in close collaboration between Bosch and Institut für Strahlwerkzeuge [Institute for Laser Beam Tools, IfSW] at Stuttgart University and Forschungsgesellschaft für Strahlwerkzeuge, [Research Company for Beam Tools, FGSW]. Within the framework of the project process efficiency was increased to such an extent that these processes can now be used economically.

The special feature of ultrashort impulse laser technology compared to continuous laser material processing is the compression of laser energy into very tiny time segments of 5 to 100 picoseconds (ps). One picosecond is a millionth of a second. In this short time the laser output is compressed in an impulse of several hundred megawatts and applied to the work piece. As a comparison, this is the output generated by an average sized power station. The time is so short that the material of the work piece vaporizes without getting hot or even melting, because thermal processes are much slower. This is why this method is also called "cold" laser milling. This enables high precision milling with no undesired melting burrs or thermal side effects.

Figure 1a shows a cross section of a V-shaped structure with 10,000 times longer impulses (150 ns) with the unavoidable melting burr and the associated reworking, while Figure 1b shows how precise the process is at 10 picoseconds. This new technology with ultrashort laser impulses was used for the first time in the world in 2007 in the Bosch factory in Bamberg, Germany to produce exhaust-gas sensors. The sensors are made of a special ceramic material and measure exhaust gas values faster and more accurately than previous sensors. This enables the car's pollutant emissions to be reduced further by means of the engine control system. Bosch is currently introducing the processing technology with ultrashort laser impulses in the production of common rail injectors for diesel fuel injection systems. This allows very small micro-channels to be produced, which ensure that the complete system remains leak-proof even with injection pressures of up to 2,000 bar (Figure 2 top). Thanks to this technology injection systems will be even more reliable, more efficient and more environmentally friendly than in the past.

Experts predict that the market volume for ultrashort impulse lasers in 2008 could be as high as 260 million dollars. Reducing the costs of short impulse lasers and further increasing their efficiency are major requirements for opening up new areas of application. Germany is one of the leaders in this field of optical technologies, not least because of its far-sighted research policy.
Figure 1a: Cross section of structures with ns impulses.
Source FGSW mbH
Figure 1b: Cross section with ps impulses.
Source FGSW mbH
Figure 2: Diesel fuel injection system with micro-channel
Source Bosch