Brillouin-Interferometry

Knowing the elastic properties of geo-materials is crucial to determine the mineralogical composition of the Earth's interior. The Brillouin scattering lab at the Helmholtz Centre Potsdam GFZ enables us to determine the velocities of sound waves in minerals, glasses and fluids to pressures of the deep Earth. We use Brillouin scattering - the inelastic scattering of laser light by thermal atomic vibrations (phonons) in the samples under investigation. We measure the frequency shift of the scattered light which is related to the speed of sound in the sample material as a function of pressure, temperature and orientation inside the sample. From these data we are able to determine the full elastic tensor which controls the elastic response of a material subject to a mechanical action. This corresponds, for instance, to the periodic deformation caused in rocks by seismic waves propagating through them.
We have built, in collaboration with DESY HASYLAB, a new Brillouin spectroscopy system at PETRA III, the third generation synchrotron source in Hamburg. The new systems allows one to combine acoustic velocity measurements and density measurements by X-Ray diffraction at the same experimental conditions at the extreme conditions beamline P02.2, next to the Brillouin scattering laboratory.