稀土掺杂碲钨酸盐玻璃光纤的光谱与中红外激光性能

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题名	稀土掺杂碲钨酸盐玻璃光纤的光谱与中红外激光性能
作者	李科峰
学位类别	博士
答辩日期	2011
授予单位	中国科学院上海光学精密机械研究所
导师	胡丽丽
关键词	稀土离子碲钨酸盐玻璃光纤 ~2 μm光纤激光宽带发光
其他题名	Spectroscopic and mid-infrared lasing performance of rare earth doped tungsten tellurite glass fiber
中文摘要	本论文的主要目的是研究适用于~2 μm激光输出的玻璃和光纤，以及通信窗口宽带光放大的光纤基质材料。通过对碲酸盐玻璃成分的探索，研究出一种高玻璃化转变温度，低热膨胀系数的新型碲钨酸盐玻璃，并以此为基础制备了双包层玻璃光纤。在Tm³⁺单掺碲钨酸盐玻璃光纤中实现了瓦级~2 μm激光输出。论文第一章首先综述了稀土掺杂固体激光的发展与应用，概括了碲酸盐玻璃的研究进展以及光纤激光用碲酸盐玻璃的特点，然后提出了本论文的研究内容和研究思路。论文第二章主要介绍了实验方法、样品制备、性质测试、光谱理论计算等。论文第三章研究了不同WO₃含量对TeO₂-WO₃-La₂O₃(TWL)玻璃热学性能和光谱性质的影响。发现WO₃的增加可以提高TWL玻璃的热稳定性，降低玻璃的热膨胀系数。WO₃含量为30 mol%时，玻璃转变温度T_g为457 ℃，DTA曲线上无析晶开始温度T_x，玻璃的热稳定性最好，且热膨胀系数也最小，为122.4×10^-7/℃。研究结果表明，相比于TeO₂-ZnO基玻璃，TWL玻璃具有优良的热学性能和光谱性质，是一种实现~2.0 µm激光输出的理想玻璃基质材料。在确定了Tm³⁺掺杂量之后，系统研究了不同浓度Yb³⁺离子共掺对其红外发光和上转换发光的影响，发现Yb₂O₃含量为2 mol%时，1.8 μm处发光最强。研究发现Yb³⁺到Tm³⁺离子的能量传递效率达89%。Yb³⁺到Tm³⁺的能量传递系数为 3.67×10^-40 cm⁶/s。通过计算，发现Tm³⁺离子在TWL玻璃中1835 nm处的最大增益系数为3.6 cm_-1。论文第四章以新型TeO₂-WO₃-La₂O₃(TWL)玻璃为基础，根据光纤相关参数，设计出光纤芯层、内包层、外包层玻璃配方，研究了大块玻璃熔制工艺，制备出光学均匀性优良的碲钨酸盐玻璃。通过研究预制棒加工及光纤拉制等多项关键技术，成功拉制出碲钨酸盐玻璃双包层光纤，其直径~220 μm，芯径~20 μm，芯层数值孔径为0.14，内包层直径~62 μm，内包层数值孔径为0.29。在1310 nm处的传输损耗<2.9 dB/m。研究发现，与块体玻璃中2微米发光相比，2微米波段的光纤光谱向长波方向移动。另外，光纤光谱的荧光半高宽FWHM比块体玻璃中小，随着泵浦功率的增加，FWHM显著减小，从~220 nm降至~160 nm。当泵浦功率达到500 mW时，~1900 nm处的发光显著增强并变窄，表明在Tm³⁺掺杂碲钨酸盐玻璃双包层光纤中，1900 nm处最易发生粒子数反转。激光实验中采用芯径为18 μm，长度40 cm的Tm³⁺掺杂碲钨酸盐玻璃双包层光纤，测得激光阈值为1.46 W，在泵浦功率6.95 W时输出功率达到1.12 W，斜率效率为~20%，对应的光~光效率大于16%。通过研究Tm³⁺-Ho³⁺离子的能量传递过程和2微米荧光光谱，分析得出Tm³⁺-Ho³⁺共掺TWL玻璃的最佳浓度为1 mol% Tm₂O₃，0.5 mol% Ho₂O₃。以此为基础制备了Tm³⁺-Ho³⁺共掺TWL玻璃光纤。与在块体玻璃中相比，光纤中Tm³⁺离子1.9 μm处发光强度大为减弱，由此可见在光纤中Tm³⁺向Ho³⁺进行的能量转移效率更高。随着光纤长度的增加，Tm³⁺离子³H₄→³F⁴跃迁的1.46 μm发光逐渐增强，说明由于Ho³⁺离子的上转换发光，Ho³⁺向Tm³⁺的反向能量转移随光纤长度增加而增大。论文第五章首先以新型Bi₂O₃-GeO₂-Na₂O (BGN)玻璃为基础，通过调整Er³⁺和Tm³⁺离子的掺杂浓度，获得了1300-1650 nm范围内很宽的发光峰，荧光半高宽达~160 nm。通过研究温度对宽带发光的影响，详细阐述了Er-Tm离子之间的能量传递过程。研究发现，在BGN玻璃中，Er³⁺-Tm³⁺ 能量传递效率达77%。通过研究Er³⁺单掺和Er³⁺-Tm³⁺共掺BGN玻璃的上转换发光，发现在Er³⁺-Tm³⁺共掺玻璃样品中，随着Tm³⁺离子浓度增加，绿光发光强度显著减弱，红光强度略有增强。上转换发光强度随掺杂浓度的变化，进一步证明BGN玻璃中Tm³⁺和Er³⁺离子之间存在有效的能量传递。通过研究Tm³⁺-Ho³⁺离子间的能量传递过程，在合理的掺杂浓度下(Tm₂O₃ 1.0 mol%，Ho₂O₃ 0.2 mol%)，在TWL玻璃中实现了1600-2200 nm范围内的宽带发光，荧光半高宽达370 nm。研究发现， TWLTm2Ho玻璃中前向能量传递系数C_Tm-Ho约为后向能量传递系数C_Ho-Tm的22倍，表明Tm (³F₄) 向Ho (⁵I₇)进行了有效的能量传递。由 C_Tm-Tm≈2.47C_Tm-Ho可以推断，Tm (³F₄)→Ho (⁵I₇)之间的能量传递与Tm³⁺离子³F₄ 能级的激发迁移之间存在竞争，这也促使³F₄→³H₆(1.8 μm)和⁵I₇→⁵I₈ (2.0 μm)荧光强度易于达到平衡，从而实现1600-2200 nm的宽带发光。
英文摘要	The motivation of this study is to search glass hosts suitable for ~2 μm fiber laser and broadband communication system. A novel tungsten tellurite glass double cladding fiber with high T_g and low coefficient of thermal expansion (CTE) is invented. A watt level cw fiber laser at ~2 μm is demonstrated in a 40 cm length of this fiber. Effects of WO₃ on the thermal stability and spectroscopic properties of Tm³⁺ doped TeO₂-WO₃-La₂O₃(TWL) glasses are studied. It is found that the thermal stability of TWL glasses is improved with the increment of WO₃ content. For the glass containing a WO₃ of 30 mol%, the glass transition temperature (T_g) is 457 ℃, while the onset crystallization temperature (T_x) is not observed in DTA curve, and the CTE decreases to 122.4×10^-7/℃ (30-300 ℃). The maximum emission cross-section of Tm³⁺ in TWL glass is 9.6×10^-21cm². Evaluated from the thermal and spectroscopic properties, TWL glass is a promising host material for ~2.0 µm glass laser. After fixing the optimum Tm³⁺ doping concentration, Yb³⁺ is introduced into the glass as the sensitizer. The 1.8 μm emission characteristic and energy transfer processes of Tm³⁺ and Yb³⁺ in TWL glass are analyzed, the results show that the Yb³⁺ ions can transfer their energy to Tm³⁺ ions with a large energy transfer coefficient, and a maximum efficiency of 89% is achieved. The maximum gain coefficient at around 1835 nm is calculated to be 3.6 cm^-1. Based on the novel TeO₂-WO₃-La₂O₃(TWL) glass, the core, inner cladding and outer cladding glasses of the fiber are designed and fabricated with high optical quality. A Tm³⁺-doped tungsten tellurite glass double cladding fiber with the propagation loss < 2.9 dB/m at 1310 nm is developed. The fiber had a ~20 μm core diameter with a numerical aperture (NA) of 0.14, and a ~62 μm inner cladding diameter with a NA of 0.29. Compared to the 1.8 μm emission in bulk glass, the peak shifts to longer wavelength in the fiber due to radiation trapping where light is absorbed from the ground state to the ³F₄ level and then re-emitted. It is also observed that the peak narrows in fiber with the increment of the absorbed pump power. It is important to note the emission intensity at ~1900 nm shows a significant enhancement when the absorbed pump power reaches 500 mW, which means the population reversion is easily occurred at around 1900 nm in this Tm³⁺ doped tungsten tellurite glass double cladding fiber. A watt level cw fiber laser at ~2 μm is demonstrated in a 40 cm length of this fiber pumped by a commercial 800 nm laser diode. The maximum output power of the fiber laser reaches 1.12 W. The slope efficiency and the optical-optical efficiency with respect to the absorbed pump power are 20% and 16%, respectively. The lasing threshold is 1.46 W and the lasing wavelength is centered at 1937 nm. In Tm³⁺/Ho³⁺ codoped TWL glass, the optimum doping concentration is Tm₂O₃ 1.0 mol% and Ho₂O₃ 0.5 mol%, respectively. It is found that the emission intensity of Tm³⁺:1.9 μm in the fiber decreased drasticly compared to the bulk glass, which indicates the higher energy transfer efficiency from Tm³⁺ to Ho³⁺ in the fiber. With the increment of the fiber length, the 1.47 μm emission increases, which means there is a back energy transfer from Ho³⁺ to Tm³⁺. Er³⁺-Tm³⁺ co-doped novel bismuthate glasses (Bi₂O₃-GeO₂-Na₂O) with different [Tm]/[Er] ratios have been synthesized and a fairly flat and broad emission covering the wavelength range of 1300-1650 nm corresponding to the ³H₄→³F₄ transition of Tm³⁺ and ⁴I_13/2→⁴I_15/2 transition of Er³⁺ can be observed with the excitation of 800 nm laser diode. A full width at half maximum (FWHM) of ~160 nm is obtained by codoping the glass with 1.0 wt% of Tm₂O₃ and 0.3 wt% of Er₂O₃. The energy transfer processes between Tm³⁺ and Er³⁺ in BGN glasses are analyzed in detail. The temperature dependence of the broadband emission spectra in Er³⁺-Tm³⁺ co-doped BGN glass is also studied, which is helpful to understand the energy transfer processes. For the Er³⁺ single doped BGN glass, the excitation from ⁴I_15/2 to ⁴I_9/2 generates upconversion fluorescence ²H_11/2→⁴I_15/2 (525 nm), ⁴S_3/2→⁴I_15/2 (545 nm), and ⁴F_9/2→⁴I_15/2 (665 nm) due to the excited state absorption (ESA) and the energy transfer upconversion (ETU) processes. For the Er³⁺/Tm³⁺ co-doped glasses, the intensities of green emissions reduce significantly as Tm³⁺ concentration increases, while the intensity of red emission increases slightly. The intensities of green and red emissions affected via the addition of Tm³⁺ into Er³⁺ doped BGN glasses, which indicates the presence of efficient energy transfer between both ions. The energy transfer efficiency from Er³⁺ to Tm³⁺ is 77%. The infrared emission of Tm³⁺-Ho³⁺ codoped TWL glass shows a broad and flat luminescence in the range of 1600-2200 nm corresponding to the ³F₄→³H₆ transition of Tm³⁺ and ⁵I₇→⁵I₈ transition of Ho³⁺. The FWHM and the relative intensity of the 1.8 μm and 2.0 μm emissions depend on the [Tm]/[Ho] concentration ratio. A FWHM of ~370 nm is abserved by codoping the TWL glass with 1 mol% Tm₂O₃ and 0.2 mol% Ho₂O₃. The energy transfer processes of Tm³⁺ and Ho³⁺ are analyzed in detail. The forward energy transfer C_Tm-Ho is about 22 times larger than the backward energy transfer C_Ho-Tm, a large ratio of C_Tm-Ho/C_Ho-Tm indicates that energy transfer from Tm (³F₄) to Ho (⁵I₇) in TWLTm2Ho is quite efficient. A competition between the Tm(³F₄)→Ho(⁵I₇) energy transfer and the migration of excitation through ³F₄ states is highly expected because of our calculation that C_Tm-Tm≈2.47C_Tm-Ho, which makes the intensity balance between the ³F₄→³H₆ (1.8 μm) and ⁵I₇→⁵I₈ (2.0 μm) transitions happened easily.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15673]
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	李科峰. 稀土掺杂碲钨酸盐玻璃光纤的光谱与中红外激光性能[D]. 中国科学院上海光学精密机械研究所. 2011.

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