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ransparent glass-ceramics are still on the top in the field of functional photonic materials used in optical fiber technology. Generally, the glass-ceramic (GC) material consists of glass and suspended in amorphous volume nanocrystals doped with lanthanide ions. The controlled degree of crystallization is carried out in the process of heating materials at a specified temperature and at the right time of the experiment. Due to this, the glass-ceramic optical waveguide structures thus get better emission parameters (high quantum efficiency) compared to analogous amorphous structures, while maintaining the high optical quality. Nowadays, the GC optical fibers technology is complicated and consist many steps, wherein each stage of the experiment the material is thermal treated (melting → bulk annealing → drawing fibers → heat-treatment). As a result, this process is very complex and controlling the size and density of nanocrystals is difficult.
In our work we focused on the possibility to develop glass-ceramic optical fibers by one-step fabrication process. This is an innovative approach to the issue of nucleation, as well as to the growth of nanocrystals during the cooling of the vitreous mass. In fact, the crystallization process control through selecting the rate of cooling from the supercooled liquid zone during optical fibre drawing has not yet been investigated systematically. The influence of selected crystallization mechanism (nucleation and growth rates) on luminescent properties of GC is a kind of alternative approach to the currently used multi-step methods. Our experiment opens new possibilities for obtaining transparent glass-ceramic optical fibers with a high-density of nanocrystals embedded in their structure.
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