Engineering of Thermally Stable Oxyfluorophosphate and Tellurite Glasses with Enhanced Spectroscopic Properties for Optical Waveguide Applications

Abstract

Glasses, due to their amorphous structure and compositional versatility, are widely used in various technological applications related to photonics, particularly when doped with rare earth ions such as Er<SUP>3+</SUP> ions. Among different glass families, phosphate and tellurite glasses stand out due to their favorable properties such as their low melting temperatures and their high rare earth solubility, making them promising candidates for optical fibers and photonics devices.

In this thesis, the structure–property relationships in Er<SUP>3+</SUP>-doped oxyfluorophosphate and tellurite glasses is investigated, focusing on the effects of compositional modifications and thermal treatment on the thermal and spectroscopic properties of the glasses. This work specifically examines the potential of silver addition to enhance the thermal stability of these glasses, facilitating their processing and enabling the formation of glass-ceramics and precipitation of silver nanoparticles.

The addition of silver was found to enhance the thermal stability of glass by depolymerizing the two investigated glass networks, which consequently led to a reduction in upconversion properties. The enhancement of spectroscopic properties was demonstrated through thermal treatment, due to the precipitation of CaF<SUB>2</SUB> crystals in oxyfluorophosphate glasses and Bi<SUB>4</SUB>TeO<SUB>8</SUB> crystals in tellurite glasses. Depending on the temperature and duration of the thermal treatment, Ag nanoparticles were found to also precipitate in both glasses. Optical fibers were successfully drawn from these new glasses and showed effective light guidance. Finally, the tellurite glasses were found to be promising for waveguide fabrication by ion exchange process.

This comprehensive study lays the groundwork for future optimization of rare earth-doped glasses, highlighting their potential for photonic, biomedical, and sensing applications. The findings contribute valuable insights into glass design strategies to improve performance and durability, advancing the field of functional glass materials.