Coherent spectroscopy as a new luminescent materials characterisation tool

稀土掺杂材料在LED和照明、激光和闪烁材料以及太阳能电池中的能量转换器中的应用具有极大的兴趣。 近年来，特别是三价稀土离子掺杂的材料作为量子信息存储与处理、医学成像和高稳定性激光锁定等方面的材料引起了人们极大的兴趣。后者是直接关系到显着的窄均匀线宽，或等效的三价稀土金属离子的光学跃迁的长相干寿命，以及它们的长寿命的光谱空穴。 特别是Eu 3+非常适合窄均匀线宽的观察。由于均匀线宽/相干寿命对激活剂离子的局部环境内的外部扰动（例如由局部无序引起的缺陷、波动自旋或低频振动模式）极其敏感，因此它们的值在名义上等效的材料中可以变化几个数量级。因此，它们允许对局部环境进行非常灵敏的探测，例如通过研究光子回波。然而，到目前为止，对相干特性的研究主要集中在高质量的块体单晶上。然而，最近的研究表明，光子回波发射可以在高散射粉末中观察到。因此，在这个项目中，我们打算利用相干光谱作为材料表征工具，这将最终有助于改善材料性能，例如在高性能磷光体中。它的应用将提供有关材料的局部化学环境的信息，这是传统光谱学无法获得的。通过不同的制备方法制备的含Eu 3+和Eu 2+的样品的相干性质的系统研究，结合常规的光谱学和额外的表征方法，将揭示相干性质和局部环境之间的关系，并最终有助于改善光学材料的合成设计，例如高性能荧光粉。在第一步中，模型系统Y2 O3：Eu 3+将被研究，这是已经使用传统的光谱学研究。这些研究将扩展到Y2 SiO 5：Eu 3+，这是量子计算的可能候选者。最后，该方法也将在Eu 2+掺杂的材料上进行测试，以研究是否可以获得用于改进Eu 2+掺杂的发光材料的重要信息，尽管相干寿命相对较短。通过这项研究，我们希望有助于更好地了解当地环境对光学材料性能的影响。

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.