2μm光学薄膜的设计、制备以及飞秒激光损伤特性研究
文献类型：学位论文
| 作者 | 刘娜 |
| 学位类别 | 硕士 |
| 答辩日期 | 2010 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 王英剑 |
| 关键词 | 2μm 波长 光学薄膜 水吸收 光学性能 飞秒激光 激光损伤 |
| 其他题名 | Investigation of design, preparation and femtosecond pulse laser-indued damage for 2 μm wavelength optical coatings |
| 中文摘要 | 2μm波段处于水的强吸收带， 2μm光学薄膜中的微气孔很容易被H2O填充，从而影响薄膜整体的折射率和消光系数，导致薄膜光学性能下降，引起光学薄膜破坏，限制了激光系统的整体性能。因此，随着2μm全固态激光器的迅速发展，研制出性能优异的2μm波段光学薄膜元件显得越来越重要。 本文首先在没有考虑薄膜材料水吸收的情况下，设计并采用电子束蒸发（EBE）技术和双离子束溅射（DIBS）技术制备了2μm波段高反膜和波长分离膜，并分析了膜层内的场强分布。利用DIBS制备出的薄膜光谱曲线与设计要求更吻合，薄膜的光学性能更好。 研究了EBE制备的ZrO2、TiO2和Al2O3单层膜的吸潮特性，并计算出上述薄膜材料在2μm波段的折射率和消光系数。发现考虑水吸收后，薄膜在2μm波段吸收较大，折射率存在反常色散。并以此基础设计了ZrO2/SiO2 2.1μm高反膜，相比于不考虑水吸收的设计结果，它与实际制备的光谱曲线更吻合。认为EBE制备的光学薄膜不够致密，容易吸附水汽，严重影响了2μm波段薄膜的光学性能。对薄膜进行退火处理后发现，薄膜的折射率增大，堆积密度升高，薄膜更加致密，进而可以降低2μm波段光学薄膜对水的敏感性。 研究了沉积温度对EBE制备的TiO2和Ta2O5单层膜光学性能的影响。发现适当的沉积温度，可以降低薄膜在2μm波段的吸收。选取致密度高、化学计量比充分的镀膜材料可以制备出孔隙率较小、折射率较高、吸收较小的2μm波段光学薄膜。 研究了飞秒激光作用于不同薄膜材料、不同工艺制备的2μm波段不同种类光学薄膜的损伤特性。通过分析损伤阈值和损伤形貌发现EBE制备的光学薄膜膜层不致密，容易吸附水汽，当2μm飞秒激光作用于薄膜时，水汽强烈的吸收激光能量，导致薄膜极其容易破坏。对于相同工艺条件下制备的光学薄膜，薄膜材料带隙和薄膜内部场分布是影响损伤阈值的主要因素。在以上分析的基础上，提出了改善2μm波段光学薄膜飞秒激光损伤阈值的途径。 |
| 英文摘要 | At the wavelength of 2μm region, the strong water absorption exists in optical coatings with porous microstructure, which affects the refractive index and extinction coefficient about the coatings, results in optical properties degradation, causes the coatings damage and limits the laser system performance. Therefore, with the rapid development of 2μm wavelength region all solid-state lasers, it is very important to improve performances of 2μm optical coatings components. Firstly, 2μm high-reflection (HR) coating and wavelength separation coating were designed with the coating materials not considerring the water absorption, and were deposited by electron beam evaporation (EBE) and dual ion beam sputtering (DIBS), and the field distributions of the coatings were analyzed. It was found that using the coating materials with the great ratio between high and low refractive index, 2μm optical coatings with the great reflective bandwidth and the low field intensity could be prepared. Moreover, compareing with EBE, the spectral curve about 2μm optical coatings deposited by DIBS was more consistent with the design requirements. By studying water absorption properties of ZrO2, TiO2 and Al2O3 monolayers deposited by EBE, refractive index and extinction coefficient at 2μm wavelength region were calculated. The results showed that coatings at 2μm wavelength region had the large absorption and anomalous refractive index dispersion after considering the water absorption. By designing ZrO2/SiO2 2.1μm HR coating once more, the results considering water absorption was more in line with the prepared results than that not considering water absoption. It was concluded that optical coatings prepared by EBE had low-density structure and easily adsorbed moisture, which seriously impacted the optical properties of coatings at 2μm wavelength region. By annealing, refractive index and packing density of coatings could be improved, which made optical coatings at 2μm wavelength region have low sensitivity for water molecules. Influences of the deposition temperature on optical properties of TiO2 and Ta2O5 monolayers deposited by EBE were investigated. It was found that the appropriate deposition temperature could reduce coatings absorption at 2μm wavelength region. In addition, choosing high-density, the enough stoichiometric ratio coating materials, optical coatings with low-porosity, high-refraction index and low-absorption at 2μm wavelength region could be prepared. Femtosecond pulse laser induced damage on different 2μm wavelength optical coatings deposited using different coating materials and preparation technologies was studied. By means of analyzing the damage thresholds and the damage morphologies, it was found that optical coatings prepared by EBE had low-density microstructure and easily collected water molecules, which causes the strong water absorption for 2 m wavelength under femtosecond pulse laser irradiation and coatings damage. In addition, the bandgap energy of coating materials and the electric field distribution in the optical coatings prepared by same conditions were two main factors which affected 2μm femtosecond laser damage. Moreover, some methods for improving the laser-induced damage thresholds of optical coatings at 2m wavelength region were put forward. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16674]  |
| 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 | 刘娜. 2μm光学薄膜的设计、制备以及飞秒激光损伤特性研究[D]. 中国科学院上海光学精密机械研究所. 2010. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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