Spectroscopic Properties And Comparative Investigation In Multi-composition Broadband Erbium-doped Glasses

The Er³⁺-doped SiO₂-based fiber amplifier(EDFA) is widely used in tremendous capacity fiber communication system because of its some excellent characteristics such as high gain, lower noise figure and so on. However, the bandwidth of the conventional SiO₂-based EDFA is limited (³5nm), which only covers with a narrow bandwidth at 1.53μm communication window, and can not meet the demand of the modern dense wavelength division multiplexing (DWDM) optical network systems. So it is urgent to investigate new glass host which can amplify C+L band signal synchronously. Besides, as the development of the WDM techonoly and the miniaturization of fiber amplifier, it needs to improve unit length gain. So high-doped glass fiber hosts are needed. Recently, there has been a great deal of interest in Er³⁺-doped tellurite- and bismuth-based glasses, which were considered to be a well-known promising candidate for 1.53μm broadband optical amplifiers, because they exhibit a large stimulated-emission cross section and a broad emission bandwidth at the third communication window, and has a better rare earth dissolvability.The spectroscopic properties were studied in in multi-composition broadband erbium-doped tellurite and bismuth glasses,respectively. The effects of concentration quenching, radiative trapping and OH- groups absorption were studied and compared with Er³⁺-doped tellurite- and bismuth-based glasses. Based on these, the glasses with the composition of TeO₂ and Bi₂O₃ coexistence were prepared and the spectroscopic properties were analyzed. The results are important for the choise of the glass host for the EDFA.In chapter one, the development of optical communication, WDM system and EDFA are introduced. The characteristic of rare earth doped laser glass material,Er³⁺-doped broadband glass host are also introduced in this section. At last, the purpose,content and significance of this dissertation are presented .In the chapter two, the theoretical backgrounds which will be used in this thesis are introduced, including Judd-Ofelt theory, McCumber theory and nonradiative transition theory.In the chapter three, the influence of Ce³⁺ on the spectroscopic properties of Er³⁺-doped TeO₂-ZnO-La₂O₃ glass was investigated. It was found that the fluorescent intensity of ⁴I₍13/2 level, stimulated emission cross section and FWHM of Er³⁺ ion were increased, while the upconversion intensity under 975 nm excitation was suppressed with the dopping of Ce³⁺. The lifetime variations of the ⁴I_11/2 and ⁴I_13/2 level with Ce³⁺ were analyzed.In the chapter four, B₂O₃ component was introduced into the Er³⁺-doped Bi₂O₃-GeO₂- Ga₂O₃-Na₂O glasses which applied for 1.53um-band broad amplifications. With the introduction of B₂O₃ component, the lifetime of Er³⁺:⁴I_11/2 level and ⁴I_13/2 level were shortened, and the 1.53μm quantum efficiency of Er³⁺ ions decreased. The 1.53um fluorescence intensity was somewhat weakened, but its effective spectral width was further broadened.In the chapter five, the effect of concentration quenching and radiative trapping of Er³⁺-doped TeO₂-ZnO-La₂O₃ and Bi₂O₃-B₂O₃-GeO₂-Na₂O glasses were analyzed. It was found that there was stronger effect of concentration quenching and radiative trapping in TZL glasses than in BBGN glasses with the same Er³⁺-doped concentration.In the chapter six, a series of Er³⁺-doped TeO₂-ZnO-La₂O₃ and Bi₂O₃-B₂O₃-GeO₂-Na₂O glasses with different concentration of OH- groups were prepared and the interaction between the Er³⁺ ions and OH- groups was investigated and compared. Infrared spectra were measured in order to calculate the exact concentration of OH- groups in samples. The observed increase of the fluorescence lifetime with the oxygen bubbling time has been related to the reduction in the OH- concentration evidenced by infrared (IR) absorption spectra. The obtained values of interaction constant KOH-Er which indicates that the interactions between Er³⁺ ions and OH- groups in bismuth-borate glass is stronger than in tellurite-borate glass under the same removing hydroxyl group treatment.In the chapter seven, the spectroscopic properties of Er³⁺/Yb³⁺-doped TeO₂-Nb₂O₅-Bi₂O₃ glasses were analyzed as a function of Nb₂O₅ content. It was found that theΩt (t=2,4,6) parameters of the Er³⁺ ion increased first and then decreased as a function of Nb₂O₅ content. The value of FWHM×σe of Er³⁺ in this work is larger than those of silicate, phosphate, and the thermal stability of this glass is better, indicating this glass is a promising host material for broadband amplification.Finally, all the results of the present work are outlined, and it is suggested that something should be done in the next stage.