高功率固体激光（HAP SSL）晶体Nd:GGG和Cr, Nd:GGG的生长、光谱和激光性能的研究
文献类型：学位论文
| 作者 | 姜本学 |
| 学位类别 | 硕士 |
| 答辩日期 | 2007 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 赵志伟 |
| 关键词 | Cr，Nd：GGG 晶体生长 光谱性质 高功率热容激光 |
| 其他题名 | Study on growth, spectral and laser performance of high average power solid-state laser crystals Nd:GGG and Cr, Nd:GGG |
| 中文摘要 | 掺Nd离子的GGG晶体是高功率固体热容激光器的理想材料。Nd：GGG晶体与Nd：YAG激光晶体相比，具有一系列优异的性质：Nd：GGG晶体容易在平坦固液界面下生长，不会产生由于小面生长所引起的杂质、应力等集中的核心，整个横截面都可以有效利用，容易得到应用于大功率激光器的大尺寸板条和片状元件；Nd离子在GGG中的分凝系数为0．52，远大于在YAG中的分凝系数（仅为0．18），所以可以实现在晶体中的高浓度掺质；同时可生长大尺寸（大于1scm）单晶，并且Nd：GGG晶体具有好的力学和化学稳定性、高的热导率、宽的泵浦吸收带和长的荧光寿命，泵浦光的吸收和储能性都较好，可实现连续和脉冲式激光运转。Nd：GGG已成为大平均功率固体激光器的首选材料之一。所以生长并研究大尺寸的Nd：GGG晶体，是一项非常有意义的应用基础研究，将不论是对国防还是对民用都具有非常深远的影响。我们用中频感应加热提拉在国内首次成功的生长了直径为61mm的Nd：GGG晶体。对晶体生长过程中已出现的Ga2O3原料挥发、螺旋生长、容易引入包裹体等几个问题进行了理论和实验分析：通过对原料的前期处理，采用固相合称法，共沉淀等方法在较低的温度下合成了GGG多晶相，基本上解决了Ga2O3原料的挥发问题。生长过程中通过对比发现：通入气氛为Ar气＋O2气时，晶体生长时的挥发较弱。通过在原料中加入Ca，Mg等二价离子解决了晶体生长时一的螺旋生长问题；分析认为，晶体中包裹物的成因是由于生长过程中Ga2O3原料的挥发形成了局部的熔体组分富Gd2O3，从而有可能形成Gd4Ga2O9和Gd3GaO6。；另一种包裹物的成因可能是由于02与Ir金属发生反应。通过测量Nd：GGG晶体的吸收光谱，研究了Nd离子在晶体中的径向和纵向分布。实验结果表明，Nd离子在晶体中径向均匀分布，说明晶体生长是在平界面下进行的。沿纵向方向，由于Nd离子在晶体中的分凝系数小于1，所以随着晶体的生长，Nd离子的浓度在变大。研究了Nd离子在GGG和YAG晶体中的浓度碎灭方式，找出了Nd离子在两种晶体中浓度碎灭效应不同的原因。首次生长并系统研究了Cr，Nd：GGG的吸收光谱和荧光光谱特性。晶体的吸收光谱中分别存在中心位于440nm和610nm的cr3+离子的4A2-4Tl和、4T跃迁，峰值位于0．53、0．59、0．75和0．81pm的Nd离子的几个吸收带：中心位于1．064nm的吸收带对应于c尹"离子的3T2-3T1跃迁。从吸收光谱上看，Cr，Nd：GGG晶体把cr4＋离子的可饱和吸收特性与Nd3＋离子的激光增益特性结合到一起，而且适合于二极管（LD）泵浦。这样有利于实现用Cr4＋离子作为被动调Q开关的Nd3＋离子的自调Q激光输出。并且cr,Nd：GGG晶体的荧光强度比Nd：GGG晶体的要小，而且其荧光寿命比Nd：GGG晶体的要短，随掺入Cr4＋离子浓度的增加而进一步降低，说明，尽管Cr4＋离子对Nd3＋离子有浓度碎灭效应，这对于晶体的激光输出还是有一定好处的。用SOSIun的钦宝石激光器泵浦lmm厚的Nd：GGG晶体微片获得了激光输出，输出激光波长为l．062um，输出的最大平均功率为122mw，系统的激光效率高达20％，泵浦阂值为65mw。 |
| 英文摘要 | Nd-doped GGG crystal is an ideal material used for high-average power heat-capacity solid-state laser(HAP SSL). As we know that the Nd:GGG crystal has a series advantages compared with Nd:YAG which is widely used in solid state laser system when price is unconcerned: Nd:GGG can be grown core-free up to 15cm in size and superior optical quality while Nd:YAG single crystal is limited to a few centimeters; The concentration of Nd ions in GGG can be up to 4 at.% and even more, while in YAG it is limited to 1.5%; The segregation coefficient of Nd ions in GGG crystals is 0.52 while 0.18 in Nd:YAG crystals; And also it has large absorption and emission cross-sections, small Stokes shift, and long fluorescence time; What's more, there is week concentration quenching of Nd ions when it take the place of Gd ions. By now only a few countries like USA can grow large Nd:GGG crystals, so for China it is really necessary to have this techniques. And also it is really a valuable thing to grow large diameter Nd:GGG crystals. Large sized ( O 61mm) highly perfect Nd:GGG crystals were grown successfully by RF-heating Czochralski method. The causes of spiral growth, crystal cracks and inclusion formation were discussed theoretically and experimentally. Causes of inclusions formation are due to the serious volatilization of Ga2C>3 and the reaction between Ir and O2. When growing GGG crystal with large diameters, spiral growth often occurs. In order for the process to produce uniform crystal growth, the growing crystal must support a meniscus of liquid above the level of the surrounding melt. This meniscus is held up by the surface tension between the liquid and the growing crystal.- It has been established that impurities in the meniscus region lower the surface tension of the liquid phase. By the addition of Ca2+ and Mg2+ ions into the melt, a counteracting effect is produced causing the meniscus to remain in contact with the growing crystal. The absorption spectra of Nd:GGG crystals were measured. By comparing the difference of absorption coefficient we get the difference of Nd concentration. Along the radius the concentration of Nd ions in Nd:GGG crystals is near unity which means the solid-liquid surface is flat during crystal growth. Because the segregation coefficient of Nd ions in GGG crystals is only 0.52, the concentration of Nd ions becomes higher along the growth axis. For the first time we grown and studied the Cr, Nd: GGG crystals. The absorption of Cr4+, Nd3+ in GGG crystal occurs in the wavelength range 300-1000nm. There are absorption bands at 400nm and 610nm which correspond to the 4A2~^4Ti and 4A2~>4T2 transitions of Cr3+ ions. The absorption band around 1350nm corresponds to the 3A2~^3Ti transition of Cr4+ ions. With the increase of the concentration of Cr, the fluorescence lifetime reduces dramatically. From the point of the energy transfer, the mechanism was analyzed. The introduction of Cr4+ into Cr, Nd: GGG crystal is good for storing more energy, and is suitable for outputting of high power per pulse. Using 808nm Ti:Sapphire laser as pumping sources, the laser at 1.062 u m of lmm thickness Nd:GGG crystal microchip has been demonstrated. The maximum output power is 122mW, the efficiency is as high as 20%, and the threshold is 65mW. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16641]  |
| 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 | 姜本学. 高功率固体激光（HAP SSL）晶体Nd:GGG和Cr, Nd:GGG的生长、光谱和激光性能的研究[D]. 中国科学院上海光学精密机械研究所. 2007. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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