Polymer-based composite active fiber doped with Tm3+ and Yb3+ — Technology and luminescent properties in VIS spectral range

摘要

Summary form only given. Recent years observed significant development of the technology of luminescent materials for application in light sources (both coherent and incoherent) operating in the visible part of the spectrum. Undoubtedly, the most spectacular results have been obtained in the field of wide bandgap semiconductor lasers, considerable progress has been also observed in solid state lasers based on crystalline or glassy hosts with frequency conversion. Despite this results, however, there is still a room for development of entirely new types of active media, like e.g. composite polymers doped with optically active nanocrystals. Such a materials may potentially benefit from excellent luminescent properties of RE3+ doped nanocrystals and good optical and thermo-mechanical properties of polymer matrices enabling drawing the optical fibers based on these composites. In such a design nanocrystalline environment provides the protection of active ions from interactions with highly energetic phonons of polymer matrix and simultaneously, polymer host encapsulating nanoparticles shields these from interactions with OH- groups and other contaminations. In this work we summarize the results of our research on design and development of the first PMMA-based optically active composite fiber, activated with rare-earth ions introduced in a form of active nanocrystals. The set of Tm3++Yb3+ doped nanocrystalline samples based on oxide and fluoride crystals of different dopant concentration was synthesized using precipitation method. All manufactured samples were carefully examined by means of classical optical spectroscopy - in particular excitation and emission spectra together with luminescence dynamic profiles have been recorded and analyzed with specific focus on up-conversion excitation schemes. The optimal pumping wavelengths were experimentally verified using a unique pressure tuned semiconductor laser diodes. For samples with optimal luminescent properties the bulk composites based on PMMA polymer doped with Tm3++Yb3+:YF₃ nanocrystals were manufactured and carefully tested.