LASERS IN ACTION
Photosynthesis secrets
revealed by laser
New research shows how a laser technique Alternative laser-based techniques for
reveals the way the sun’s energy moves inside gathering such information do already exist,
plants, unravelling some of the inner workings but require the sample to be exposed to the
of this efficient solar energy process. laser light for a long period, which may lead
The research, published in Physical Review to sample degradation. They also require
Letters, explains how the team, led by Dr Ian much more intensive computer processing.
Mercer from the School of Physics at The researchers needed a very powerful
University College Dublin, who is a visiting and stable laser in order to get the new
researcher at Imperial College London, used a approach to work efficiently and accurately.
laser to probe a sample of a protein found in They used the Astra laser at the Science and
bacteria, called LH2, which was provided by Technology Facilities Council’s Rutherford
the University of Glasgow. This bacterial Appleton Laboratory (RAL).
protein was used because it harvests light in With this laser, a map can be captured
the same way as photosynthetic plant with a single pulse of laser light meaning
proteins. By illuminating the sample with a that full information can be gathered prior
combination of high-power laser pulses all to, or during, a chemical reaction. The
derived from the same laser, the researchers technique can also be used to characterise
obtained a map of bright spots on a camera in high-value, delicate samples, because only
a tiny fraction of a second. The position of a small quantity of sample is required.
each spot corresponds to a unique angle of And with one thousand laser pulses
light emitted from the sample and this directly available per second from the laser, there is
relates to how electrons in the protein respond potential for rapid automated sample
to the laser light and to each other. characterisation.
Institute delivers laser innovation
The Fraunhofer Institute for Laser get by with as few additive materials as
Technology has unveiled a range of laser- possible, and should under no circumstances
based research projects that push the influence or contaminate the materials. As an
boundaries of laser capabilities. alternative to conventional joining
The LIFTEC joining process (patent techniques, laser welding offers a number of
pending) works by heating a component, or innovative solutions featuring high welding
a part of it, by laser radiation, which passes speeds, narrow weld seams and special
through the plastic joining partner. The process variants for joining transparent
component is pressed onto the plastic part plastics.
under mechanical pressure, then heated, and A series of new beam sources enables laser
finally pushed into the plastic by further characteristics to be specially adapted to these
mechanical pressure. Provided that a suitable tasks. Highly advanced microsystems with
component geometry has been selected, a complex welding contours for medical
solid, positive bond is formed after cooling. engineering and biotechnological applications,
It is essential to the process that the such as a new type of microfluidic chip with
component should have a higher melting very narrow and closely spaced channels,
point than the plastic joining partner. make great demands on joining technology.
Suitable materials include metals, ceramics The new chip has to be furnished with a cover
and temperature-resistant plastics. film, for which the welding seam must be no
The institute has also developed a more than 100µm wide.
contour-welding method for microsystems. The new TWIST (Transmission Welding
Medical products and components in the by Incremental Scanning Technique)
bio-engineering and bio-analysis sector have contour-welding method developed by the
to be made from highly bio-compatible Fraunhofer Institute meets these stringent
materials and the joining method employed requirements, producing high-quality
has to meet special requirements. It has to welding seams at high process speeds.
www.lasersystemseurope.com issue 2 • LASER SYSTEMS EUROPE 7
LSEspr09 pp04-07 News.indd 7 3/3/09 10:41:59
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