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题名	稀土离子掺杂铽镓石榴石晶体的生长及性能研究
作者	陈喆
学位类别	博士
答辩日期	2015
授予单位	中国科学院上海光学精密机械研究所
导师	杭寅
关键词	磁光晶体 浮区法生长 提拉法生长 铽镓石榴石晶体 稀土离子掺杂
其他题名	Study on growth, spectra and properties of Re3+ doped Tb3Ga5O12 single crystals
中文摘要	石榴石晶体作为一种优良的磁光材料，是法拉第旋光材料研究领域的热点。其中最常用最典型的是钇铁石榴石（YIG），但在400-1100nm通信波段，YIG或者掺杂YIG晶体的透光性能不佳，磁光优值低，限制了其在可见光-近红外波段的应用。因此近年来新型磁光材料的探索研究主要集中在可见光-近红外波段具有更高法拉第旋光系数的磁光单晶材料。铽镓石榴石(Tb3Ga5O12,TGG)作为磁光材料具有良好的磁光效应，其在可见-近红外光区内具有高的Verdet 常数和低的吸收系数，广泛适用于波长400-1100nm（不包括470nm-500nm）的法拉第隔离器和高功率激光磁光器件。 铽镓石榴石晶体相较于铽铝石榴石晶体(Tb3Al5O12,TAG)具有一致熔融特性，因而可以用传统的提拉法制备，然而用提拉法生长铽镓石榴石晶体却比较困难，由于组分Ga2O3的挥发，很难获得高光学质量的晶体。光学浮区法(optical floating zone method)晶体生长装置是为新晶体探索而研制的快速晶体生长设备。该方法具有生长快、无需坩锅、无污染等优点，对于一些生长困难(包含提拉法不能生长的晶体）或者易被坩埚污染的晶体显示出很大的优越性。该方法丰富了晶体生长手段，有利于缩短晶体的探索研究周期。因此我们分别采用光学浮区法和提拉法生长了纯的TGG晶体，系统地研究了TGG晶体的物理性能、热学性能、光学性能及磁光性能。 TGG相较于TAG在通信波段其Verdet常数较低（在1064nm处为36rad/mT，比TAG低约20%左右）。由于法拉第隔离器需要偏振光产生45°的旋转角度，而旋转角度与材料的Verdet常数和长度有关，因此低的Verdet旋光常数意味着需要尺寸更大的晶体才能满足旋转角度，这极大地增大了器件的不稳定性，因为通光方向的晶体长度越长，其光速的退偏度越大（材料的消光比越低），光束的质量越差，器件的灵敏性也越差。 随着光纤通信技术的发展，对信息传输质量和容量方面的要求越来越高。从材料研究角度来看，必须设法提高作为隔离器核心部件磁光材料的性能，使其在通信波段具有高的Verdet旋光常数和光传播系数(低的吸收系数）。目前提拉法生长稀土顺磁性稀土离子掺杂的铽镓石榴石晶体未见报道，而其在400-1100nm波段的旋光性能也未探究过，因此该课题是磁光晶体的重要研究方向。通过Re3+掺杂改善材料的磁光性能，有望探索获得更高Verdet常数、低吸收系数的TGG基晶体，为拓展磁光器件在可见-近红外波段范围的应用奠定基础。 本文重点选取了可用提拉法生长的铽镓石榴石晶体作为研究对象，主要研究了纯的Tb3Ga5O12晶体以及Ce3+、Pr3+、Nd3+掺杂的Tb3Ga5O12晶体的生长、光学性能、热学性能、激光损伤阈值和磁光性能，主要包括以下几个方面的内容： 1．浮区法制备TGG晶体的研究 采用光学浮区法制备出Φ7×30mm3的TGG单晶。确定了光学浮区法生长TGG单晶生长中的各个参数（温度梯度、生长速度）和生长条件。目前已经掌握了光学浮区法生长TGG单晶的生长工艺。通过XRD、XRC、XPS等方法对得到的TGG晶体进行了相应的结构质量分析。利用电子探针X射线显微分析技术对浮区法生长的TGG单晶进行了轴向和径向组分分析和 ICP元素检测，结果表明浮区法生长的TGG单晶的元素组成接近于化学计量比，表明该方法生长过程中G2O3的挥发少，单晶的组分均匀性高。 2. 提拉法制备TGG晶体的研究 采用提拉法生长了尺寸为Φ25×30mm3的TGG单晶，晶体光学质量良好，无开裂，无包裹物，无散射光路。通过XRD、XRC等方法对得到的TGG晶体进行了相应的质量分析并对TGG晶体的基本物理性质（密度、比热、热扩散系数和热导率）进行了实验研究。测试了提拉法制备的TGG单晶在波长1064nm下的法拉第旋光效应以及晶体的法拉第旋转角随波长、磁场强度的变化趋势。同样考察了在不同温度下TGG晶体在1064nm下Verdet 常数的变化，TGG晶体在室温下的Verdet 常数为37-40 radT-1m-1。测试了TGG晶体的激光损伤阈值（输出光为Nd:YAG的脉冲激光，输出频率为1Hz，脉冲宽度为8ns），提拉法生长的TGG晶体在1064nm处的损伤阈值为13.75 J/cm2，高于我们购买的商品化的TGG晶体（11.06 J/cm2)。 3.提拉法生长掺Ce3+:TGG晶体的研究 采用提拉法生长了Ce3+掺杂浓度为1.0at.%的TGG晶体，晶体尺寸约为Φ30×25mm3。晶体光学质量良好，无开裂，无包裹物，无散射光路。测得了Ce3+在TGG晶体中的分凝系数为0.404，并测试了晶体的结构、热学性质、光学性质（透过率，折射率，热光系数等），测试了晶体在532nm、632.8、1064nm处的Verdet 常数和在1064nm处的弱吸收系数，其中Ce3+掺杂TGG晶体在3个波段的Verdet 常数分别为242.5、164.3、53.2radm-1T-1，较纯TGG晶体的Verdet常数显著提高。其中PCI检测Ce3+掺杂TGG在1064nm处的弱吸收系数为1800ppm/cm，磁光优值为29.6×105rad/T，较纯TGG(24.3×105 rad/T)提高了21.8%。测试了晶体在25-500 ℃的热导率，综合以上测试结果表明Ce3+:TGG晶体相较纯TGG是一种性能更加优良的磁光材料，有望取代TGG成为400-1100nm波段的法拉第旋光材料。 4. 提拉法生长 Pr:TGG，Nd:TGG晶体的研究 采用提拉法生长了Pr掺杂浓度为3.0at.%的Φ25×50 mm3的Pr:TGG晶体以及掺杂浓度5at%的Φ20×28 mm3Nd:TGG晶体。晶体的外形完整、透明、无宏观缺陷和无散射，具有高光学质量。Nd3+、Pr3+的掺入不会引起TGG基质晶体结构的改变，仍为立方晶系Ia3d空间群。测得了Pr:TGG晶体的密度，比热，热扩散系数，热导率和激光损伤阈值等重要热学性质，研究了晶体在400-1100nm处的光学性能，测试了晶体的透过谱，吸收谱，弱吸收系数等基本光学参数。测试了Pr: TGG以及Nd:TGG晶体的Verdet常数随波长的变化，尤其是在400-1000nm波段中，Pr: TGG以及Nd:TGG晶体的旋光常数均有明显提高。Pr: TGG晶体在3个波段的Verdet常数分别为286.3、182.4、60.3radm-1T-1，主要工作波段的Verdet常数比纯TGG晶体提高30%左右；Tb3-xNdxGa5O12 晶体在1064nm下的Verdet 常数为41radT-1m-1，在532，633nm处的Verdet 常数分别为225radT-1m-1，145radT-1m-1。
英文摘要	Garnet crystal as an excellent magneto-optical material has been becoming the research focus of the Faraday rotation material. However, in the 400-1100nm communications band, YIG has poor light transmission properties and low magneto-optical merit, limiting its use in this band. Therefore, exploring new magneto-optical material in recent years has focused on the visible - near infrared magneto-optical single crystals having a higher coefficient of Faraday rotation. Terbium gallium garnet (Tb3Ga5O12, TGG) as a magneto-optical material has excellent magneto-optical effect, a high Verdet constant and low absorption coefficient in the visible and near-infrared spectral region, so it becomes an ideal materials for wavelength 400-1100nm (not including the 470nm-500nm) of visible-near infrared laser magneto-optical device, and it is widely used in Faraday isolators and high-power laser magneto-optical devices. Terbium gallium garnet has consistent melt characteristics compared with terbium aluminum garnet crystal, therefore can be prepared by traditional Czochralski(Cz) method, and Cz method is also the most-common studied, but terbium gallium garnet crystals grown by the Cz method have some difficulties due to the volatile components Ga2O3, so it is difficult to obtain a high optical quality crystals. Optical floating zone method is a fast crystal growth equipment to explore and develop new crystals. This method has fast growth, without crucible, pollution, etc., for some growth difficulties (including crystals cannot be grown by Cz method or be easily contaminated) showed great superiority. This method enriches the crystal growth methods, exploration and research will help shorten the period crystals, accelerate the process to grow crystals. Therefore, we use an optical floating zone method and the Cz method to grow pure TGG crystal, systematic study of the physical properties of the crystal, thermal properties, optical properties and magneto-optical properties. Terbium gallium garnet crystals has low Verdet constant (36rad/mT at 1064nm, 20% lower) compared to the terbium aluminum garnet crystal in optical communications band. Since the Faraday isolator requires 45 degree polarized light rotation angle, and the rotation angle of the material has relation with its Verdet constant and length of the crystal, therefore low constant of Verdet means that it will take longer crystal material to meet the crystal rotation angle, which greatly increases the instability of the device applications (the lower extinction ratio of the material with the high instability), because the longer length of the light through the crystal orientation, the light depolarization degree becomes larger and of the quality of the beam becomes worse, and so the sensitivity of the device. With the development of optical communication technology, information transmission quality and capacity requirements gets higher and higher. From materials research point of view, we must find ways to improve the performance of a magneto-optical isolator core material so that it has a high Verdet constants and light propagation coefficient (low absorption coefficient) at the communication band. Currently paramagnetic rare earth ions doped terbium gallium garnet crystals have not studied, it has not been explored in 400-1100nm band of optical performance, so the subject is an important research direction of magneto-optic crystals. In this thesis, we investigated the growth、thermal spectra and magneto-optical performance of Ce3+, Pr3+ and Nd3+ doped Tb3Ga5O12 single crystals, and also focused on the laser induced damage threshold and thermal conductivity in the Re3+ doped Tb3Ga5O12 single crystals. The main contents of this thesis are as follows: 1.Research of preparing TGG?crystal by optical floating zone method. we prepared TGG crystal with a diameter of about 6-7mm, length of about 30mm by this method. Determining the growth conditions and the individual parameters (temperature gradient, growth rate)of growing TGG crystals by optical floating zone method .We has mastered the growth technical of optical floating zone method. By XRD, SEM, XPS and chemical corrosion and other methods to get TGG crystal the corresponding quality analysis. By using the electron probe X-ray method to get a analysis of axial and radial component of TGG crystal by the floating zone method. We also investigated a ICP elemental testing of TGG components, the results showed that the TGG crystal obtained by floating zone method has a higher composition stoichiometric ratio, indicating that this method has less volatile growth process, so the single crystal chemical homogeneity is higher. 2. Research of growing TGG?crystal by Cz method Using the Cz method to gain a size of 25×30mm3 of TGG crystal with good quality crystal optics, no crack, no inclusions, no scattered light path. TGG crystals were obtained corresponding quality analysis by XRD, XRC, XPS and chemical corrosion and other methods , experimental results show that the TGG Cz grown crystals with high optical quality. The basic physical properties of the TGG crystal (density, specific heat, thermal diffusivity and thermal conductivity) were studied experimentally. We have tested the TGG crystal prepared by the two method of Faraday rotation effect under 1064nm wavelength and crystal rotation angle trends with wavelength and intensity of the magnetic field. We also studied TGG crystal versing at different temperatures under 1064nm Faraday rotation coefficient. Testing the laser damage threshold of TGG crystal, test conditions are the output light of Nd: YAG pulsed laser (1064nm), the output frequency of 1Hz, pulse width 8ns.Cz grown TGG crystal damage at 1064nm threshold of 13.75 J/cm2, higher than our purchase of the commercialization of TGG crystal (11.06 J / cm2). 3. Research of growing Ce3 + doped TGG crystal by Cz method Grown by Cz method Ce3+ doped TGG crystal with dimensions of approximately 30×25mm3, measuring the Ce3+ segregation coefficient in TGG crystals and tested the crystal structure, thermal properties, optical properties (transmittance, refractive index, thermal coefficient, etc.) and Verdet constant at 532,632.8,1064nm of the crystals, the weak absorption coefficient at 1064nm, while Verdet constant of Ce3 + doped TGG crystal in three bands were 242.5, 164.3, 53.2 rad/Tm, relatively larger than the pure TGG crystal. PCI detect which weak absorption coefficient of Ce3 + doped TGG crystal at 1064nm is about 1800ppm, magneto-optical quality of 29.6×105rad/T, purer TGG (24.3×105 rad / T), improved by 21.8%. Test the thermal conductivity of the crystal at 25 ~ 300℃and the crystal damage threshold at 1064nm, The larger figure of merit point out the superior magneto-optical characteristics of Ce3 + doped TGG, therefore it has potential to cover the increasing demand for new and improved Faraday rotators in the VI-NIR region. 4. Research of growing Pr3+, Nd3+ doped TGG crystals by Cz method Growing Pr3+, Nd3+ doped TGG crystals by Cz method, Pr doping concentrations 3.0at% of Φ25 ×50 and the doping concentration of 5% Nd: TGG crystal with the size of Φ20×28. The crystals are with completely shape, transparent, non-macroscopic defects, no scattering and high optical quality. Nd3+, Pr3+ incorporated in the matrix does not cause a change to the TGG crystal structure, still cubic system Ia3d space group. We have measured Pr: TGG crystal density, the basic physical properties of heat, thermal diffusivity and thermal conductivity and laser damage threshold. Also have studied the optical properties of crystals at the 400-1100nm tested through the crystal spectrum, absorption spectrum weak coefficient basic optical parameters. Tested Verdet constant of Pr3+, Nd3+ doped TGG crystal changes with wavelength, especially in the 400-1000nm wavelength band. Pr: TGG crystal optical constants obtained were significantly improved. Pr: TGG crystals were 286.3,182.4,60.3radm-1T-1 in the Verdet constant of three bands, Verdet constant of the main operating band of higher than about 30% pure TGG. The Verdet constant of Tb3-xNdxGa5O12 crystal at room temperature at 1064nm was 41radm-1T-1, at the Verdet constant 532,633nm were 225,145radm-1T-1, respectively.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15944]
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	陈喆. 稀土离子掺杂铽镓石榴石晶体的生长及性能研究[D]. 中国科学院上海光学精密机械研究所. 2015.

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