铋掺杂玻璃的超宽带荧光与光放大性能的研究
文献类型：学位论文
| 作者 | 任进军 |
| 学位类别 | 博士 |
| 答辩日期 | 2008 |
| 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 红外发光 超宽带光放大 光纤放大器 |
| 其他题名 | Bismuth-doped glasses with ultra-broadband luminescence and optical amplification |
| 中文摘要 | 随着计算机网络及其它新的数据传输业务的飞速发展, 提高光波分复用系统的传输容量和速率成为迫切需要。 传统的稀土离子掺杂光纤放大器，由于受到f-f跃迁的限制，增益带宽一般为35nm左右，严重限制了波分复用系统的进一步发展。因此，对超宽带光纤放大器的研究显得十分重要。目前对光纤放大器放大区域的展宽主要有两种方法：一种是开发拉曼光纤放大器(RFA), 通过多泵浦的复用达到宽带放大的目的, 但泵浦数目的增多又给其实际应用带了困难,它不仅提高了系统的成本，而且还增加了系统的复杂度。 另一种方法是利用掺铒光纤放大器( EDFA) 和FRA 相结合构造宽带放大器, 这样可以节省所需泵浦数并能在较宽(80～100nm) 的波长范围实现放大，然而，这样也会使得工艺变得非常复杂，而且还会造成严重的光信号损失。因此开发单波长激发新型超宽带光纤放大器具有重要意义。 铋掺杂玻璃在400～1100nm波长范围内的任意波长处激发，会发射覆盖1000～1700nm波长范围内的超宽带红外发光，荧光的最大值半高宽（FWHM）约300nm, 荧光寿命约为几百微秒。铋掺杂玻璃这种超宽带光学性能表明它是一种非常有前途的潜在超宽带光放大材料，它们很有可能成功解决目前稀土离子掺杂光纤放大器和拉曼光纤放大器所面临的放大带宽不足和多波长激发的缺点。本论文以铋掺杂玻璃在光通信窗口区域的超宽带荧光和光学放大为课题，系统的研究了玻璃成份, 工艺参数，和激发波长对铋掺杂玻璃的超宽带荧光和光放大性能的影响，研究了吸收光谱和荧光光谱特性，提出了铋掺杂玻璃的红外发光机理，优化了玻璃组份，成功的实现了铋掺杂玻璃的光放大。 在碱土金属硅酸盐玻璃中，观察到发光峰在400nm, 640nm 和1300nm附近的3个发光带，位于400nm的发光来自Bi3+, 640nm的发光来自Bi2+离子，而1300nm发光的起源至今尚不能确定。但是随着碱性的增强1300nm发光强度明显减弱，当碱金属氧化物加入玻璃后，1300nm的红外荧光出现瘁灭, 这些荧光强度的减弱是因为玻璃碱性的增强降低了红外活性中心的浓度。根据光学碱度理论，我们认为红外活性中心是低价的铋离子，例如Bi+。 以前关于铋掺杂玻璃红外发光的报道中，Al3+, Ga3+，和B3+ 等3价离子被一致认为是红外发光必不可少的成分，但并不清楚这些离子的真正作用。为了研究清楚这些离子的作用，我们设计了铋掺杂的BaO-SiO2玻璃体系并研究了它们的红外发光特性，发现在没有Al3+等3价离子存在的情况下，也有红外发光，否定了以前认为Al3+等3价离子是铋的红外发光必不可少的组份这一推断，并否定了红外发光来源于Al3+·Bi+复合体这一观点，我们认为Al3+在铋掺杂的玻璃中起了增加和分散红外活性铋离子的双重作用。 在铋掺杂的锶锗酸盐玻璃中，在980nm激发下，我们发现了最大值半高宽（FWHM）约510nm的超宽带红外发光，当锶被钙和镁取代后，在980nm激发下FWHM逐步减小到315nm，这些发光由3个高斯峰组成。而在808nm激发下,铋掺杂碱土金属锗酸盐玻璃的红外发光由2个高斯峰组成，并且随着碱土金属的变化Sr2+→Ca2+→Mg2+，红外荧光的FWHM改变趋势是225nm→300nm→330nm, 这种变化趋势正好与980nm激发时的变化趋势相反。我们认为FWHM的变化是由于铋掺杂玻璃中存在几个化学环境不同的铋红外活性中心, 这些活性中心在不同的玻璃中相对含量的不同引起了荧光宽度FWHM的变化。 经过系统的实验研究，我们优化了玻璃成分和制备工艺，在808nm激发下，成功地在铋掺杂的锗酸盐和锗硅酸盐玻璃中，实现了1272～1348nm波段的光学放大，并且实现了在980nm激发下1300nm波长处的光放大。铋掺杂玻璃的这种超宽带发光和光放大性能，表明这种新型超宽带材料极有可能成为超宽带光纤放大器的增益介质，超宽带可调谐激光器，和超短脉冲激光光源。 OH-基团对稀土离子的红外荧光有很强的瘁灭作用，为了了解OH-对铋掺杂玻璃红外发光的影响并改善红外发光性能，我们对磷酸盐和硅酸盐玻璃进行了除水实验，发现当OH-的浓度减少后，铋掺杂玻璃的荧光强度和荧光寿命明显增强，实验结果表明，除水工艺对铋掺杂玻璃的实际应用有重要意义。 铋掺杂玻璃在激发波段的吸收较弱，严重影响了铋掺杂玻璃的红外发光强度和光放大性能，为了提高铋掺杂玻璃对激发光的吸收效率，我们在铋掺杂玻璃中共掺了具有高吸收率的敏化离子Yb3+。当0.8mol%的Yb2O3加入铋掺杂的玻璃中，玻璃样品在980nm处的吸收迅速增强，在980nm激发下铋的红外发光增强了23倍，但是随着Yb2O3含量的增加，红外活性铋离子的浓度迅速减小。Yb3+对铋掺杂玻璃的这种双重作用需要进一步研究，进而优化Yb3+对铋掺杂玻璃红外发光的贡献。 为了进一步证实铋掺杂玻璃的红外发光机理，除了研究光学碱度与铋掺杂玻璃红外发光之间的关系外，我们还改变了玻璃的制备温度，加入了氧化还原剂，来研究这些因素对发光性能的影响。我们发现随着玻璃制备温度的降低和氧化剂的加入，红外活性离子浓度和1300nm的荧光强度明显减弱。从制备温度，共掺氧化剂和光学碱度三个方面观察到的实验现象说明铋掺杂玻璃的红外发光起源于低价态的铋离子，同时我们又发现红外发光起源于Bi3+，Bi2+，Bi0，和BiO的可能性很小，所以我们认为铋掺杂玻璃的红外发光起源于Bi+。Bi+第一激发态到基态的辐射跃迁 产生了红外发光。 |
| 英文摘要 | With the rapid development of computer networks and other data-transmitting services, it is an urgent demand to increase the transmission capacity and bit rate of wavelength division multiplexing (WDM) system. However, the gain bandwidth of traditional rare earth doped fiber amplifiers is about 35nm, due to the restriction of f-f transition, which severely limits the further development of WDM. Therefore, it is important to develop ultra-broadband fiber amplifiers. There are mainly two ways to expand the bandwidth of fiber amplifiers. One is to develop Raman fiber amplifiers (RFA) and to expand the bandwidth by multiwavelength pumping. But the increase in pumping sources will result in the cost increment and the complication of the system, which brings much difficult for the practical application of the system. The other way is to construct hybrid fiber amplifiers by integrating Raman fiber amplifiers and erbium doped fiber amplifiers (EDFA), which can expand the bandwidth to 80~100nm width with less pumping sources. But integration of the amplifiers will result in the complication of the system and the signal loss as well. So it is valuable to develop novel amplifiers with ultra-broadband optical amplification excited by a single pumping source. Bismuth-doped glasses show ultra-broadband luminescence covering 1000～1700nm wavelength region excited within 400~1100nm wavelength region. The full width at half maximum (FWHM) is about 300nm. And the fluorescence lifetime is about several hundred microseconds. The ultra-broadband luminescence of bismuth-doped glasses indicates that these glasses may be the potential gain medium for ultra-broadband optical amplification. Maybe they could successfully overcome the deficiency of EDFA and RFA in narrow bandwidth and requirement of multiwavelength pumping, respectively. The project of this dissertation is the research on bismuth-doped glasses with ultra-broadband luminescence and optical amplification within the optical communication window. The effects of glass components, technology parameters and excitation wavelength on the ultra-broadband luminescence and optical amplification have been systematically studied. The absorption and fluorescence spectra of the glass samples were studied. The infrared luminescence mechanism of bismuth-doped glasses was proposed. The glass components were optimized. And finally, optical amplification was successfully realized. Three luminescence bands centered at about 400nm, 640nm and 1300nm were observed in bismuth-doped alkaline earth metal silicate glasses. The luminescence centered at 400nm and 640nm arose from Bi3+ and Bi2+, respectively. The origin of the luminescence centered at about 1300nm is still unclear. But the luminescence intensity at 1300nm obviously decreased with the increase in the basicity of the glass host. Once the alkali metal oxide was introduced into the glasses the luminescence intensity decreased sharply. The decrease in the luminescence intensity was due to the decrease in the infrared active centers with the increment in the basicity of the glass. Based on the optical basicity theory, the infrared luminescence was ascribed to the bismuth in low valence state such as Bi+. Trivalent ions such as Al3+, Ga3+, B3+ and so on were considered indispensable for the infrared luminescence from the bismuth-doped glasses in the past reports，but the roles of these ions in the luminescence were still unclear. In order to clarify the effects of these ions on the luminescence, we devised bismuth-doped BaO-SiO2 glass system and study their luminescence. Intense infrared luminescence could be still observed in the glasses without these ions, which disprove the conclusions that the trivalent ions such as Al3+, Ga3+, B3+ and so on were indispensable for the infrared luminescence from the bismuth-doped glasses and that the luminescence origins from Al3+·Bi+ complex. But we think that Al3+ had the performance to increase the concentration of the infrared active bismuth ions and disperse the infrared active bismuth ions. We observed the ultra-broadband infrared luminescence with the largest FWHM (about 510nm) in bismuth doped strontium germanate glasses excited at 980nm. When strontium was replaced by calcium and magnesium, the FWHM of the glass samples gradually decreased to 315nm excited at 980nm. In the case of 808nm excitation, the luminescence from bismuth-doped alkaline earth metal germanate glasses could be fitted into two Gaussian peaks and the FWHM of the luminescence changed in the tendency 225nm→300nm→330nm with the change of alkaline earth metal ions Sr2+→Ca2+→Mg2+. The change tendency of the FWHM with alkaline earth metal ions in the case of 808nm excitation was reverse with that in the case of 980nm excitation. We think the change of FWHM arose from the multiple sits of the active centers. The active centers in different sits had variable quantity in different glasses, which resulted in the change of FWHM with glass components. We optimized the glass components and the fabrication technology after systematical experiments. And finally, we successfully realized optical amplification within 1272～1348nm wavelength region in bismuth-doped germanate and germanosilicate glasses, excited at 808nm. We also realized optical amplification at 1300nm in these glasses excited at 980nm. The ultra-broadband luminescence and optical amplification performance of the glasses indicate that they may be the potential tunable laser sources, ultra-short pulse laser sources and gain medium for the ultra-broadband fiber amplifiers. OH- has severe quenching effects on the infrared luminescence from rare earth ions. To know about the quenching effect of OH- on the infrared luminescence from bismuth-doped glasses and to improve the infrared luminescence performance, we conducted water-removing experiments for the bismuth-doped phosphate and silicate glasses. We found that when OH- was reduced the luminescence intensity and the fluorescence lifetime had obvious increment. It indicated that the water-removing technology was very important for the practical application of bismuth-doped glasses. The absorptivity of bismuth-doped glasses at the excitation wavelength is weak, which severely restricted the infrared luminescence intensity and the optical amplification performance. In order to improve the absorption efficiency, we codoped sensitizer ions Yb3+ with high absorptivity to increase the absorption of the excitation sources. When 0.8mol% Yb2O3 was introduced into the glasses, the absorptivity at 980nm increased greatly and the luminescence intensity increased about 23 times excited at 980nm. But the concentration of the infrared active bismuth ions decreased with the increment in Yb2O3 content. The double effects of Yb3+ on the luminescence should be further studied and optimized. To further clarify the origin of the infrared luminescence from bismuth-doped glasses, besides studying the relationship between the optical basicity and the luminescence, we have changed the fabrication temperature of the glasses and introduced oxidant into the glasses to study the change of the luminescence with these factors. We found that with the decrease in the fabrication temperature and the introduction of oxidant, the concentration of the infrared active centers and the luminescence intensity at 1300nm decreased obviously. Based on the optical spectra change with the fabrication temperature, the introduction of codoped oxidant and the optical basicity, the infrared luminescence from bismuth-doped glasses should be ascribed to the bismuth in low valence state. We also found that it was almost impossible that the infrared luminescence arose from Bi3+, Bi2+, Bi0，and BiO, so we think the luminescence should arise from Bi+. The radioactive transition from the first excited level to the ground level of Bi+ emits the infrared luminescence． |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15482]  |
| 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 | 任进军. 铋掺杂玻璃的超宽带荧光与光放大性能的研究[D]. 中国科学院上海光学精密机械研究所. 2008. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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