Aim of the project is to develop fiber core materials that enable laser-active optical fibers with enhanced efficiency by preventing energy transfer caused by rare-earth (RE) ion clustering. In conventional silica-based fibers, RE-ion clustering leads to cross-relaxation, reducing fluorescence and laser efficiency. Conventional methods like Al2O3 wet-chemical co-doping or using Y-Al-Garnet rods in rod-in-tube preforms result in variable random RE ion distribution, crystallization risks, and significant SiO2 diffusion, impacting core composition and refractive index profile.
The proposed approach utilizes a zeolite-based method to achieve a homogenous distribution of RE ions, involving ion exchange to embed RE ions into two different regularly arranged, crystalline cage structures in Zeolite X. These structures maintain a minimum distance between RE ions and prevent clustering.
The project will explore two main strategies. Firstly, Yttrium (Y3+) will be used as a optically passive component in the ion exchange process due to its comparable ionic radius and coordination to “dilute” RE. Secondly, incomplete or multi-step exchange processes will be investigated using passive ions like alkaline earth metals, La³⁺ or Al3+ which differ in size and may selectively occupy the two zeolite cages.
Experimental work will focus as well on pre-sintering of the ion-exchanged zeolite to fix the ion positions, fabrication of fiber preforms and test fibers. Characterization will involve structural analysis and spectroscopic fluorescence lifetime measurements to assess RE ion clustering, crystallization behaviour and refractive index profiles.
The potential application of the material lies in high-efficiency fiber lasers, particularly for high-fluorescence performance. Apart from that, insights into ion exchange kinetics, cluster prevention in aluminosilicates and enhanced understanding of doping mechanisms will be new valuable knowledge.