掺镱晶体激光特性研究及激光自动准直系统设计
文献类型：学位论文
| 作者 | 于海波 |
| 学位类别 | 硕士 |
| 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 | 冷雨欣 |
| 关键词 | LD泵浦 掺Yb3+激光晶体 调谐 自动准直 |
| 其他题名 | Study on the laser performances of Yb3+-doped laser material and automatic alignment system design |
| 中文摘要 | 随着高亮度InGaAs 激光二极管(LD)的迅速发展，其输出功率、稳定性的不断提高及成本的下降，以及人们对激光器高效、高功率、小型化、集成化的追求，适应这一泵浦波段的掺Yb3+激光晶体研究受到了人们的广泛关注。Yb3+离子是能级结构最简单的激活离子，电子构型为4f13，仅有一个基态2F7/2和一个激发态2F5/2，两者的能量间隔约为10000cm-1。由于在这个能级之上不存在任何其他激光态能级，因而可以有效地避免上能级转换、激发态吸收和弛豫振荡等激光能量损耗。而且，相比Nd3+激活离子，Yb3+离子具有更长的能级寿命，储能能力更强。更为重要的是，Yb3+离子具有更宽的吸收和发射光谱，其吸收带在900～1000nm范围，能与InGaAs LD泵浦源（870～1100nm）有效耦合，且吸收带较宽，使得LD泵浦源不需要复杂的温度控制系统；而宽的发射光谱又使得掺Yb3+激光材料更适合实现可调谐连续输出和超快激光运转。因此，掺Yb3+激光晶体是发展新型全固态低阈值、高功率和宽调谐超快激光的首选增益介质。 激光器由于温度场的随机变化、构成谐振腔的元器件的微蠕动，导致谐振腔发生变形，造成激光器发射光束的漂移。在靶场实验中，激光光束大多数都需要经过一段相当长的路径才能进入靶室；还有些实验需要相当长的数据采集时间以获得准确的实验结果。在这些情况下，激光束的微小漂移都将导致十分可观的偏差，造成实验数据的准确度下降。在微细加工领域，光束方向的稳定性更直接关乎加工的精度。因此，激光自动准直系统已经是激光实验中不可或缺的一部分。 本论文主要围绕掺Yb3+激光晶体的激光特性展开，研究了不同基质掺杂比例、不同切割方向的Yb:GYSO晶体，不同厚度的Yb:LuAG晶体,Yb:YAG激光陶瓷，Yb:YAG复合晶体的连续运转特性及波长调谐特性。同时，对激光自动准直系统也做了一定的探索。主要研究成果如下： 1. 采用波长976nm的LD作为泵浦源，对不同的基质掺杂比例、不同切割方向的Yb:Gd2xY2(1-x)SiO5 (Yb:GYSO)混晶的激光特性进行了光谱分析和实验研究。光谱分析和实验均表明，对于x=0.1的Yb:GYSO晶体，垂直生长轴切割的样品，其激光性能要明显优于平行生长轴切割的晶体；在9W的泵浦功率下，输出功率达3.13W，对应的斜效率为44.68%；在输出耦合镜T=9%，8W的泵浦功率下，得到了迄今为止Yb:GYSO晶体最大连续调谐范围：1014-1085nm。 2. 采用波长938nm的LD作为泵浦源，对不同厚度的10at.%Yb:LuAG晶体进行了光谱分析和激光实验。最大输出功率达3.23W，对应的斜效率为48.6%；在1033nm-1079nm波段实现连续调谐输出，最高转换效率达到55％。 3. 研究了LD泵浦的Yb:YAG陶瓷激光器、Yb:YAG复合晶体激光器的输出特性。在9W的泵浦功率下，Yb:YAG陶瓷激光器获得了1.63W的激光输出，对应的斜效率为23.2%。在6.15W的泵浦功率下，Yb:YAG复合晶体激光器，获得了1.354W的激光输出，对应的斜效率为25.3%。 4. 设计了一个新型的激光角度自动准直系统。通过原理上严格保证空间过两点有且只有一条直线原理的适用性，只需对一个点采样，即获得理想的准直光束输出。采样速率快，减小了系统误差并降低了成本；通过两个带压电陶瓷镜座的联动，可使光路准确回归基准的过程一步到位。 |
| 英文摘要 | With the rapid development of the high power and high brightness InGaAs laser diodes emitting at 900-980nm, the Yb3+ doped laser materials have been drawing great attentions and expected to be the most potential alternatives to the traditional Nd3+ doped ones in the near-IR spectral range. The Yb3+ has a 4f13 shell and the simplest electronic structure with just two manifold levels, the ground state 2F7/2 and the excited state 2F5/2. Therefore, Yb3+ doped gain medium have really attractive advantages, such as the low intrinsic quantum defect, a weak thermal load, the absence of luminescence quenching, upconversion, and excited-state absorption. In addition, the radiative lifetime of Yb3+ is substantially longer than that of Nd3+-doped ones (approximately 3–4 times longer) which permits greater energy-storage efficiency with diode laser-pumped systems. Moreover, Yb3+ supports broader absorption and emission spectra, which permit diode pumping with relaxed temperature controlling, wide tunability and the production of ultrashort pulses. Therefore, Yb3+-doped laser materials have been recognized as the most promising active media for diode pumped ultrafast laser with lower threshold, higher power and wider tuning range. In any kind of scientific experiments where laser pulses are involved as a main tool, unchangeable, proper alignment is the key property that determined the quality of the experimental data. In micromachining, microetching and inspection of microlithography fabrication, the spatial stability of the laser beam together with the spot size potentially limits the attainable accuracy. In most cases the laser beam has to travel a long path to reach the experimental setups, and even small deviations of the adjusted beam direction may cause unpredictable distortion of experimental data. Therefore, the auto-alignment system has become one of the most important parts during the experimental design for scientists all over the world. In this work, we focused on the spectra analysis and the laser performances of the Yb3+-doped laser crystals. The continuous wave (CW) operation and tuning ability were investigated for the new alloyed Yb:GYSO crystals with different cutting directions and different compounding ratios in the host. The same properties of two Yb:LuAG samples with different thickness were also examined. Besides that, the CW laser performances of homemade Yb:YAG laser ceramic and Yb:YAG /YAG composite crystals were explored and compared. Meanwhile, we discussed an auto-alignment method of eliminating the angle-shifting for some precise experiments. The main results are summarized as follows: 1. The laser actions of 5-at.% Yb:Gd2xY2(1-x)SiO5 (Yb:GYSO; x=0.1/0.3/0.9) crystals with different cutting directions, parallel and vertical to the growth axis, were researched. 3.13W CW output power at 1060nm with a slope efficiency of 44.68% was achieved as the best CW results. It was observed and verified theoretically that the cutting direction of the sample affected the laser output significantly. The wavelength was tuned from 1014nm to 1085nm continuously, which is the widest in Yb:GYSO so far. 2. The tuning of the diode-pumped Yb:LuAG continuous wave laser was investigated. The absorption and emission spectra of the Yb:LuAG crystal were discussed. The broad, efficient and continuous tuning range, from 1033 to 1079nm, was achieved. The CW maximum output reached 3.23W at 1050nm with the slope efficiency of 48.6%. 3. For Yb:YAG ceramic laser, 1.63W output power with a slope efficiency of 23.2% was obtained. For Yb:YAG/YAG composite crystals, the output power reached 1.354W with a slope efficiency of 25.3% by absorbing 6.15W pump power. 4. Substantial improvement was made in the design of the angle-shifting auto-alignment equipment. Only one sampling point in the light path was enough to obtain the ideal output beam. Instead of the traditional one-by-one adjusting way, we can ensure the applicability of the alignment by using two PZT controlled mounts. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16391]  |
| 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 | 于海波. 掺镱晶体激光特性研究及激光自动准直系统设计[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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