Yue Fan, Yuri N. Osetsky, Sidney Yip, and Bilge Yildiz: Onset Mechanism of Strain-Rate-Induced Flow Stress Upturn, In: Physical Review Letters, Vol. 109, Issue 13, September 28, 2012, Article 135503 [5 pages], DOI: 10.1103/PhysRevLett.109.135503: http://dx.doi.org/10.1103/PhysRevLett.109.135503

Paul Scherrer Institute (PSI) researchers have investigated the mechanisms necessary for enabling the semiconductor Germanium to emit laser light. As a laser material, Germanium together with Silicon could form the basis for innovative computer chips in which information would be transferred partially in the form of light. This technology would revolutionise data streaming within chips and give a boost to the performance of electronics. The researchers have demonstrated that Germanium must be put under strain by an external force in order to turn it into a laser material material and have thus contributed to a very active research field.

In their studies, which were performed at the Swiss Light Source (SLS) at PSI, the researchers investigated those properties of Germanium that are im- portant for the generation of laser light, and compared them with those of currently available laser materials. “We stimulate the material by means of a powerful laser and simultaneously observe the changes occurring using infra-red radiation from the SLS”, elucidates the doctoral student Peter Friedli, who carried out the decisive experiments together with scientist Lee Carroll. “To do this, we used the fact that these light pulses are only 100 picoseconds (i.e. 0.1 billionths of a second) long, allowing us to follow the relevant processes in the material; that is, the behaviour of electrons at different points in time.”

Lee Carroll, Peter Friedli, Stefan Neuenschwander, Hans Sigg, Stefano Cecchi, Fabio Isa, Daniel Chrastina, Giovanni Isella, Yuriy Fedoryshyn, Jérôme Faist: Direct-Gap Gain and Optical Absorption in Germanium Correlated to the Density of Photoexcited Carriers, Doping, and Strain, In: Physical Review Letters, Vol. 109, Issue 5, August 03, 2012, Article 057402 [5 pages], DOI:10.1103/PhysRev- Lett.109.057402:

http://dx.doi.org/10.1103/PhysRevLett.109.057402 http://www.psi.ch/

Lee Carroll, Peter Friedli, Philippe Lerch, Jörg Schneider, Daniel Treyer, Stephan Hunziker, Stefan Stutz, and Hans Sigg: Ultra-broadband infrared pump-probe spectroscopy using synchrotron radiation and a tuneable pump, In: Review of Scientific Instruments, Volume 82, Issue 6, Article 063101 [9 pages], DOI:10.1063/1.3592332: http://dx.doi.org/10.1063/1.3592332