Optical Properties Of Er/Yb Doped Borate-silicate Glass

Erbium-doped glass is one of the most important laser materials because of its key role in the optical signal amplification for 1.5μm telecommunication. To support the optical integration, increasing doping concentration is an effective solution to obtain high output power or high gain in miniaturized lasers and amplifiers. Unfortunately, most solid laser materials exhibit pronounced concentration quenching at high doping concentration. Er/Yb co-doped system has been found to be an effective method to enhance the gain due to the excellent sensitizing ability of Yb³⁺ ions. Therefore, it is of importance to study the photoluminescence properties of Er-doped and Er/Yb co-doped system in various glasses for the development for lasers and amplifiers working at 1.5 μmIn this dissertation, Er-doped, Yb-doped and Er/Yb co-doped borate-silicate laser glasses with various concentrations of Er and Yb were fabricated by high-temperature solid-state reaction. The absorption and the photoluminescence (PL) spectra, together with the lifetime of Er³⁺-⁴I_13/2 were measured. The factors affecting the PL properties, including concentration quenching, cooperative up-conversion, and energy transfer between Er³⁺ and Yb³⁺ ions, were systemically analyzed.For the Er-doped borate-silicate glasses, the dependence of PL intensity on Er concentration and lifetime has been studied. The broadening of PL spectra have been observed and the self-absorption from Er³⁺ effect on the PL measurement has been addressed. The optical parameters such as cross-section, radiative lifetime, and PL efficiency, are given based on the measurement of absorption spectra and lifetime. The dispersion effect of Y co-doping on Er³⁺ ions is also discussed. Moreover, in order to study the influence of phonon energy in glass on the Er³⁺ PL spectra, the up-conversion fluorescence of Er-doped fluoride ceramic glasses is analyzed.With the purpose of presenting some pre-information of the properties of Yb³⁺ ions for the Er/Yb co-doped glasses, the optical properties of Yb³⁺ ions in borate-silicate glasses is investigated. The absorption and emission cross-section around 980 nm is calculated based on the absorption spectra. The dependence of radiative lifetime of Yb³⁺-²F_5/2 on Yb₂O₃ concentration is also studied. The relationship between up-conversion photon and the infrared emission, together with the assistant phonon, is described according to the up-conversion fluorescence and Raman spectra analysis.For the Er/Yb-doped borate-silicate glasses, the dependence of PL intensity on Yb concentration has been investigated. The broadening of PL spectra owing to the increasing Yb concentration have been observed. The dependence of radiative lifetime calculated by Judd-Ofelt theory of Er3+ ions on Yb concentrations is compared with the measured one. The effect of Yb co-doping on Er3+ up-conversion fluorescence is also discussed with respect to the energy transfer process between Er3+ and Yb3+ ions.In order to present a systemic explanation to the energy transfer process in Er doped and Er/Yb co-doped glasses, a rate equation model for Er/Yb co-doped system has been established based on the first-handed data obtained from the measurements. Ground-state absorption, excited-state absorption, together with the energy transfer among Er3+ ions and Er3+/Yb3+ ions are included in the model. The results from the simulation are compared with the experimental ones. Through the model, a much better comprehension on the Er/Yb doped system is expressed.