| 题名 | Bi掺杂玻璃的宽带近红外荧光机理和光放大 |
| 作者 | 阮健 |
| 学位类别 | 博士 |
| 答辩日期 | 2009 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 邱建荣 |
| 关键词 | 铋离子 玻璃 宽带近红外荧光 光放大 |
| 其他题名 | Mechanism of Broadband Near-infrared luminescence and Optical Amplification in Bi-doped Glasses |
| 中文摘要 | 自20世纪90年代初，Er3+掺杂光纤放大器(EDFA)的研制成功极大地促进了波分复用技术(WDM)的广泛应用，有效地增加了光纤通信传输容量和速度，迅速地推动现代光通信网络发展。然而随着Internet技术的普及和发展，相关的数据业务呈指数模式的飞速发展，现有的基于EDFA的光纤通信系统将难以满足未来人们的需求。未来的光纤通信系统的发展需要具有更高光增益和增益带宽的宽带光纤放大器。因此，新型宽带光纤放大器的研究显得十分重要。 各国都在相关领域展开了大量相关的工作，研制开发了一系列新型稀土离子掺杂光纤放大器，如Tm3+掺杂光纤放大器(TDFA)和Pr3+掺杂光纤放大器(PDFA)。但是，稀土离子掺杂光纤放大器，由于受f-f跃迁的限制，增益带宽难以超过80nm。目前对光纤放大器的放大区域展宽主要有两种方法：一种是开发Raman光纤放大器(FRAs)，通过多级泵浦的复用来实现比传统的稀土离子掺杂光放大器更宽更平坦的增益带宽。另一种方法是利用EDFA和FRAs构造混合宽带放大器。使用这种方法可以在较低的泵浦级数实现较宽(80~100nm)的增益带宽。但FRAs本身对多级泵浦的需求，也增加了这些系统的运行成本。同时，这些系统的复杂结构也增加了操作和维护的难度。因此开发单波长激发能够覆盖全部通信波段的新型超宽带光纤放大器非常有意义。 Bi掺杂玻璃能够发射覆盖1000到1700nm波长范围内的超宽带红外发光，荧光最大半高宽（FWHM）约300nm，荧光寿命约为几百微秒。Bi掺杂玻璃的独特超宽带光学性能预示着它很有可能成功克服目前稀土离子掺杂光纤放大器的放大带宽不足和Raman光纤放大器的多波长激发的缺点，并有希望成为全新一代的超宽带光放大材料。但是，Bi掺杂材料的红外发光机理仍不明确，光放大和激光输出的报道集中在Bi掺杂石英玻璃上，关于多组分玻璃的光放大和激光输出报道较少。虽然Bi掺杂玻璃可以在808nm，980nm和1064nm等多个波长泵浦下已经实现宽带荧光发射和光放大，但Bi掺杂玻璃在上述波长的吸收截面很小，因此泵浦效率较低。 本论文以Bi掺杂玻璃的荧光机理及在光通讯窗口波长区域内宽带光放大为课题。在玻璃成份，熔制工艺，和泵浦波长等对Bi掺杂玻璃的光谱性能和光放大性能影响方面已有研究结果的基础上，我们提出了Bi掺杂玻璃的红外发光机理，并且提出利用稀土离子的共掺敏化，有效地增强了Bi掺杂玻璃的荧光性能和光放大性能。 在发光机理方面，我们针对目前对玻璃中Bi离子价态的争论（Bi+还是Bi5+），研究了不同还原剂添加量下Bi玻璃红外荧光性能的影响。通过添加适量的还原添加剂，控制玻璃在弱还原气氛下制备，可以大幅度增强Bi掺杂磷酸盐玻璃的荧光性能。这是因为适量的还原添加剂有助于Bi掺杂玻璃的中形成更多的Bi活性中心。但如果添加量过多，会导致Bi活性中心的浓度淬灭和金属铋的析出。因此，Bi掺杂玻璃中近红外荧光的来源应该归因于与低价态Bi离子（如Bi+）有关的活性中心。这种活性中心可能是有Bi离子和毗邻的结构缺陷组成的。 我们研究了混合网络体形成体效应对硅酸盐玻璃中Bi近红外荧光性能造成的影响。在研究中使用氧化锗替代氧化硅作为网络形成体，发现随着玻璃中氧化锗含量的增加，样品在808nm和940nm泵浦下的近红外荧光性能呈现出不同的变化。根据XPS谱分析，观察到的现象应归因于是Bi活性中心配位环境的改变，并推测在各个波长观察到的红外荧光与Bi活性中心周围环境的对应关系。 为了增强Bi玻璃在泵浦波长的吸收效率，我们根据敏化发光原理，提出了一些在Bi掺杂玻璃体系中共掺敏化离子通过能量转移来提高泵浦效率的方法。其中Yb-Bi共掺可以显著提高Bi离子在磷酸盐，硅酸盐，锗酸盐和锗硅酸盐玻璃中的宽带近红外荧光发射强度和宽带光放大性能，并研究了它们之间的能量转移机制。而在Nd-Bi共掺玻璃样品中则很难获得荧光性能的显著提升，利用激发光谱和时间分辨荧光发射光谱分析了这种现象产生的原因。还利用Bi离子作为敏化剂，在Bi-Tm共掺杂玻璃中显著提升了Tm3+离子的荧光性能，并通过二种离子在808nm泵浦下的共激发，实现了带宽覆盖1270~1570nm的超宽带荧光。 此外，还进行了Bi掺杂单晶的制备和光谱性能研究。在晶体中观察到了和Bi掺杂玻璃和光纤中类似的宽带红外荧光发射，接合结构分析，推测了晶体中红外荧光发射的机理。 经过对Bi掺杂玻璃的系统研究，我们加深了对玻璃中Bi红外荧光发射机理的理解，并且通过Yb-Bi共掺成功的实现了在磷酸盐，硅酸盐，锗酸盐，和锗硅酸盐玻璃中宽带荧光发射和光放大性能的增强。其中Yb-Bi共掺锗酸盐样品可以实现覆盖1300~1550nm波段的光放大，其在1300nm的最高增益系数可以达40.6 dB cm-1。Bi掺杂玻璃的这种超宽带荧光和光放大性能，预示着它极有潜力作为超宽带光放大器及可调谐激光器的增益介质。 |
| 英文摘要 | By the early 1990s, the modern optical communication networks have been highly promoted by the Wavelength Division Multiplexing (WDM) system. The WDM technique based on Er3+-doped fiber amplifier (EDFA) can provide higher transmission capacity and speed. As the rapidly development of Internet technique and its widely application in different fields, the optical communication networks requires broadband amplifiers with higher optical gain and broader gain bandwidth. Therefore, it is important to investigate and develop novel broadband fiber amplifiers. The studies on novel broadband fiber amplifiers have attracted much attention. Rare earth ions doped fiber amplifiers have been extensively studied. Several novel rare earth ions doped fiber amplifiers have been developed, such as Tm3+ doped fiber amplifier (TDFA) and Pr3+ doped fiber amplifier (PDFA). However, since the nature of infrared emission from the 4f-4f electrons transition of rare earth ions, the gain bandwidth of rare earth ions doped fiber amplifiers can not beyond 80 nm. In order to extend the bands of present fiber amplifiers, fiber Raman amplifiers (FRAs) and hybridize fiber amplifiers (HFAs) were proposed. Multi-grades pumping technique was utilized for FRAs to realized broadband amplification. But it requires high pumping consumption and has complex structure. HFAs used the complementation of EDFA and FRAs to achieve higher performance (gain bandwidth of 80-100nm) but with lower pumping consumption. However, their actual application may be baffled by the nature defects of FRAs. It is significant to develop broadband optical amplifiers with gain bandwidth covering the whole telecommunication windows excited by a single wavelength pumping source. Bi-doped glasses show broadband luminescence covering the wavelength region of 1000-1700 nm, FWHM of ~300nm, and luminescent lifetime of several hundred microseconds. Because of their unique luminescent properties, Bi-doped glasses are promising candidate materials for broadband optical amplifiers. Although lots of investigations have been focused on Bi-doped glasses, the mechanism of Bi-related near-infrared luminescence is still in controversy. Most studies of optical amplification and laser operation were concentrated on Bi-doped silica glass and fiber, but less reports on Bi-doped multi-component glass. Although pumping sources at 808nm, 980nm and 1064nm can be selected to obtain broadband luminescence and optical amplification in Bi-doped glasses, the actual pumping efficiency is relative low since the low absorption cross-section of Bi-doped glasses at those wavelengths. This thesis focused on the mechanism of the near-infrared luminescence from Bi-doped glasses and their broadband optical amplification in the telecommunication wavelengths. The effects of glass component, melting parameter, and pumping wavelength on the spectral properties and optical amplification of Bi-doped glass have been investigated. Based on those results, the mechanism of Bi-related near-infrared luminescence was proposed. A method for improving the spectral properties and optical amplification of Bi-doped glasses by utilizing the sensitization effect of rare earth ions was also proposed. In order to understand the mechanism of Bi-related near-infrared luminescence, the investigation of reducing agents additive on the spectral properties of Bi-doped glasses was proposed. Enhanced near-infrared luminescence were achieved by melting glass under controllable weak reducing atmosphere resulted by reducing agent additive. This phenomenon was ascribed the favorites of Bi-related active centers forming in the weak reducing atmosphere. However, too much reducing agent additive will lead serious concentration quenching of Bi-related active centers, and even generation of metal bismuth. Therefore, near-infrared luminescence from Bi-doped glass should be ascribed to the active centers related to bismuth ions with low valence (e.g., Bi+). Those active centers may be consisted of bismuth ions with neighboring point defect. We also investigated the mix-networks former effect on the near-infrared luminescence properties in Bi-doped silicate glass. In the study, GeO2 was selected to replace SiO2 as the networks former in the glass. With the increment of GeO2 content, the near-infrared luminescence excited at 808nm and 940nm varied in different trends. Based on XPS spectral analysis, the change of local coordination environments of Bi-related active centers was suggested to be responsible for the observed phenomena. The relationship between the near-infrared emissions observed at various wavelengths and the local coordination environments of Bi-related active centers was also proposed. In order to increase the absorption efficiency of Bi-doped glasses at pumping wavelengths, several methods were proposed based on the mechanism of sensitized luminescence. The pumping efficiency was expected to be improved through the energy transfer process by codoping sensitizers in the Bi-doped glasses. Yb-Bi codoping is one of the efficient way to enhance the broadband near-infrared luminescence and broadband optical amplification in phosphate, silicate, germanate, and germanosilicate glasses, and the mechanism of the energy transfer process was also investigated. While such phenomena can not be observed in Nd-Bi codoped glasses. The results observed in Nd-Bi codoped glasses were analyzed by luminescence excitation spectra and time-resolved emission spectra, and the reasons responsible for them were proposed. Bi ions can also be used as sensitizer to improve the luminescence properties of Tm3+ in Bi-Tm codoped glasses. By coexcitation of Tm and Bi ions in the glasses under 808nm excitation, broadband emission with bandwidth covering 1270-1570nm was obtained in the glass. In addition, Bi-doped BaF2 crystal was also fabricated and its spectral properties were also investigated. Broadband emission similar to those in Bi-doped glasses and fibers was observed. Based on the results of the structure analysis, the mechanism of near-infrared emission in the crystal was proposed. In summary, better understanding of Bi-related near-infrared luminescence was achieved by systemic investigation. Enhanced broadband luminescence and optical amplification were achieved in Yb-Bi codoped phosphate, silicate, germanate and germanosilicate glasses. The optical amplification covering 1300-1550nm was obtained in Yb-Bi codped germanate glass. The highest optical gain efficient at 1300nm reaches 40.6 dB•cm-1. Because of the ultra-broadband luminescence and optical amplification of novel Bi-doped glasses, it is potential gain media for broadband optical amplifier and tunable lasers. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15280]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 阮健. Bi掺杂玻璃的宽带近红外荧光机理和光放大[D]. 中国科学院上海光学精密机械研究所. 2009. |
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