Coherent spectroscopy as a new luminescent materials characterisation tool

• Applicant: Professorin Dr. Nathalie Kunkel
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Solid State and Surface Chemistry, Material Synthesis
• Term: from 2015 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 278731506

Rare earth doped materials are of great interest for the application in LEDs and lighting, laser and scintillation materials, and energy converters in solar cells. Lately, especially materials doped with trivalent rare earth ions have arisen much interest as materials for quantum information storage and processing, medical imaging and highly stable laser locking. The latter are directly related to the remarkable narrow homogeneous linewidths, or equivalently long coherence lifetimes of optical transitions of trivalent rare earth metal ions as well as their long-lived spectral holes. Especially Eu3+ is ideally suited for the observation of narrow homogeneous linewidths. Since the homogeneous linewidths/coherence lifetimes are extremely sensitive to external perturbations within the local environment of the activator ion, such as defects, fluctuating spins or low frequency vibrational modes caused by local disorder, their values can vary by several orders of magnitude in nominally equivalent materials. Thus, they allow a very sensitive probe of the local environment, for instance by studying photon echoes. However, so far studies on the coherence properties have mainly concentrated on high-quality bulk single crystals. Yet, it was recently shown that photon echo emission could be observed in highly scattering powder.Within this project we therefore intend to take advantage of coherence spectroscopy as a materials characterisation tool which will ultimately help in the improvement of materials properties, e.g. in high performance phosphors. Its application will provide information on the local chemical environment of materials which is not accessible with conventional spectroscopy. A systematic study on the coherence properties of Eu3+- and Eu2+-containing samples prepared via different preparation methods, combined with conventional spectroscopy and additional characterisation methods will shed light on the relation between coherent properties and local environments and ultimately help improving the synthesis design of optical materials, e.g. of high performance phosphors. In a first step, the model system Y2O3:Eu3+ will be studied, which was already investigated using conventional spectroscopy. Those studies will then be extended to Y2SiO5:Eu3+, a possible candidate for quantum computing. Finally the method will also be tested on Eu2+-doped materials in order to investigate if important information for the improvement of Eu2+-doped luminescence materials can be obtained despite of the relatively short coherence lifetimes. With this study, we hope to contribute to a better understanding of the local environments on the properties of optical materials.

• DFG Programme: Research Fellowships
• International Connection: France
• Host: Professor Dr. Philippe Goldner