Grupo de Procesado por Láser del Instituto de Óptica “Daza de Valdés”
Portada tesis Roberta Morea 2015
Author: Roberta Morea
Fecha de defensa: Mayo de 2015
Director: Jose Gonzalo de los Reyes
Universidad Autónoma de Madrid
The starting point of this thesis has been the synthesis and characterization of two different TeO2 –ZnO–ZnF2 glasses doped with Er 3+
. The structure, linear optical properties, thermal properties, and visible upconverted and near infrared photoluminescence emissions of these glasses have been studied in order to find the glass composition having the best properties for active applications. Moreover, the glasses have been doped with increasing Er3+ content (0.5-3.0 wt%) to study how this affects their photoluminescence response. The most promising TeO2 –ZnO–ZnF2 glass host was finally codoped with Er3+ -Yb 3+ or Er 3+ -Tm3+ with the aim of improving the pumping efficiency of Er 3+ ions and generating an ultra broad near infrared emission, respectively.

The characterization of rare earth doped TeO2 –ZnO–ZnF2 glasses settled the basis for one of the main objectives of this thesis, that was the production of transparent rare earth doped TeO2 –ZnO–ZnF2 glass-ceramics. This was performed by the controlled crystallisation of precursor glass samples in a temperature range determined from the experimental nucleation and crystal growth curves. Then, the microstructure, optical properties, and photoluminescence response of the transparent Er3+ doped TeO2 –ZnO–ZnF2 glass-ceramics have been studied and compared to those of the precursor glass sample. From these analyses, we have confirmed that large fraction of Er3+ ions are segregated in a fluoride crystalline phase in glass-ceramics. This affects strongly the photoluminescence response of Er3+ ions, and in particular the upcoverted red emission.
Finally, the last objective of the thesis has been the fabrication of Er doped TeO2 –ZnO–ZnF2 thin film glasses. The experience of the LPG on the fabrication of transparent tellurite film glasses by pulsed laser deposition [53] was employed to determine the appropriate parameters, such as oxygen pressure and laser fluence, for successful fabrication of transparent fluorotellurite glass films with good optical quality. Then, as-grown and annealed films have been characterized structurally and optically and compared to the bulk glass. Optimized thermal treatments allowed a strong improvement of the near infrared emission (at 1.5 μm) of fluorotellurite films without altering their glass structure. This behaviour has been related with the reduction of hydroxyl content in the annealed films.