| Tellurite glasses offer promising choices for photonics applications primarily due to their excellent optical, but also because of their good chemical and physical properties. In this thesis, we explain the strong and broad erbium emission in tellurite glasses and fibers. We study the glass network and electron-phonon characteristics of these glasses in order to understand the fundamental origin of their optical properties. In addition, we compare the absorption and emission properties of Er3+-doped tellurite and alumina-silica glasses and fibers. We show that the strength of emission properties of erbium and effects of emission in fibers are strong due to a high refractive index of tellurite glass, which increases the local field correction at an activator site and leads to larger radiative transition probabilities. It is due to this reason that rare earth ions in tellurite glasses typically have larger stimulated emission cross-sections over a large bandwidth compared to other binary oxide glasses. Tellurite glasses also have phonons up to 930 cm -1 (for WO3-TeO2), which is of great importance for non-radiative transitions from upper energy levels. At the same time, these glasses have a strong Raman scattering intensity at low phonon frequencies (100--400 cm-1). Since this frequency range corresponds to the extent of the Stark splitting of the ground state of Er3+ ions, Raman scattering allows efficient resonant electron-phonon processes. We show that these processes are the main reason for broader emission in glasses with strong phonon frequency in the 100--400 cm-1 range, particularly in WO3-TeO2. |
