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 mbHFigure 1b: Cross section with ps impulses.
Source FGSW mbHFigure 2: Diesel fuel injection system with micro-channel
Source Bosch 
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