How fast an intense laser pulse can change the electrical properties of solids is revealed by researchers from Kiel University in the current edition of Nature.
Professor Michael Bauer, Dr. Kai Roßnagel and Professor Lutz Kipp from the Institute of Experimental and Applied Physics, together with colleagues from the University of Kaiserslautern and the University of Colorado in Boulder, U.S.A., are following the course of electronic switching processes which occur within fractions of a second (femtoseconds). The results of their research may trigger future developments of custom-made and ultra fast opto-electronic components in order to increase data transmission rates or to accelerate optical switches, to name just one example of potential areas of application.
"These techniques that we have developed enables us to record films of extremely fast processes in a much more comprehensive manner than it was previously possible with similar techniques," Bauer explains. "We are able to, for example, directly track phase transitions in solids or catalytic reactions on surfaces." To record the films, the Kiel scientists used ultra short flashes of light in the soft x-ray spectral region generated with a specific laser system. Bauer: "The amount of information gained from our pictures when played back in slow motion is vast. We will get completely new insights into most relevant electronic properties of solids which are important for a variety of current and future technologies, for example, in telecommunications."
The Christian-Albrechts-Universität zu Kiel (CAU) has proven international expertise as a North German research university in the field of nanosciences and surface science, for example, in the German Research Foundation's Collaborative Research Centre 855 "Magnetoelectric Composites -- Future Biomagnetic Interfaces." Furthermore, the CAU is applying for the current round of the Excellence Initiative with the excellence cluster "Materials for Life."
Femto means "one part in a thousand million million." When, for example, molecules react with one another or when the switching states in electronic components change, processes at the atomic length scale are involved which take place on time scales of femtoseconds. Ultra short laser pulses in the so-called "soft x-ray spectral region" -- i.e. light with very short wavelengths -- enables one to make snapshots of the electronic states which are transiently formed during a switching process, for example. The shots are combined in series to deliver a film depicting such switching processes with a level of detail and a temporal resolution which could previously not be achieved.
- Timm Rohwer, Stefan Hellmann, Martin Wiesenmayer, Christian Sohrt, Ankatrin Stange, Bartosz Slomski, Adra Carr, Yanwei Liu, Luis Miaja Avila, Matthias Kalläne, Stefan Mathias, Lutz Kipp, Kai Rossnagel, Michael Bauer. Collapse of long-range charge order tracked by time-resolved photoemission at high momenta. Nature, 2011; DOI: 10.1038/nature09829
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