| 题名 | 薄膜型空间滤波器的研究 |
| 作者 | 章瑛 |
| 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 | 邵建达 |
| 关键词 | Rugate滤光片 多层介质膜 空间低通滤波 激光损伤阈值 |
| 其他题名 | Study of thin-film spatial filters |
| 中文摘要 | 在高功率激光系统中，针孔滤波器焦平面处光强>>1012W/cm2，容易诱发等离子体，产生等离子体堵孔等现象。针孔板的材料容易被激光烧蚀，作为硬边光阑，针孔容易形成低频衍射环。透镜与针孔的组合，是限制提升激光器输出功率水平的瓶颈。在空间低通滤波器中避免使用透镜，是克服针孔滤波技术上述缺点的有效措施。根据高功率激光空间滤波的特殊需求，本文研究光路中无透镜的新型滤波器――基于Rugate 薄膜、透射型多层介质薄膜以及反射型多层介质薄膜的空间低通滤波器。 本文根据传输矩阵理论，研究Rugate结构和多层介质膜组合器件实现非聚焦空间滤波，实验验证用非聚焦型空间滤波器替代针孔滤波器的可行性。研究内容和主要结论如下： 1）对Rugate负滤光片进行设计及制备，并基于磁控溅射装置详细介绍了一种通过两种材料的快速交替沉积制备Rugate薄膜的实验方法。并以此技术制备了Rugate负滤光片样品，实验测量光谱与设计光谱均能较好吻合，证明了此方法在制备Rugate薄膜方面的可行性。 2）设计了相移Rugate薄膜滤波器，根据实际制备的条件进行了误差分析，给出了制备技术需要达到的精度和所需要的薄膜材料的消光系数，计算了相应的损耗，并分析了空间滤波器内部的电场分布。 3）提出了透射型组合空间滤波器的光路，对相移型Rugate滤光片、Fabry-Perot窄带滤光片和长短波通组合滤光片进行了厚度与角分辨率的关系比较以及厚度与电场关系的比较，结果表明，在保证相同角分辨率的前提下，长短波通组合滤光片具有较低的电场强度。最后对长短波通组合空间滤波器薄膜进行了设计、制备表征和分析改进，通过光谱性能测试曲线进行计算表明，在制备过程中，当高折射率材料Nb2O5沉积厚度逐层变化量增加0.1%，低折射率材料SiO2沉积厚度逐层变化0.2%，计算的曲线与实际制备的结果更加接近。对薄膜的损伤阈值进行了测试，结果表明，用离子束溅射法制备的多层介质薄膜的损伤阈值较高，证明了透射型组合空间滤波器用在高功率激光系统中的可行性。 4）提出了反射型组合空间滤波器的设计光路，相比透射型组合滤波器件，只需要由一种反射元件就可以实现空间滤波的目的。在保证角谱选择性的前提下，降低了设计和制备的难度。另外，通过膜系设计和电场强度比较，发现此反射型组合器件具有比透射型组合器件更高的抗激光损伤阈值。为反射型介质膜组合滤波器件的制备和应用奠下了基础，对降低激光系统中的非线性自聚焦效应、缩小系统体积以及提高激光输出功率都具有重要的意义。 |
| 英文摘要 | In the high-power laser system, the intensity at the focal plane of the pin-hole filter is more than 1012W/cm2. So the plasma closure may be probably caused. And the material of the pin-hole plate is easily burned. As a hard-edge diaphragm, the low-frequency diffractive rings are likely to appear. The combination of lens and pin-hole has the performance to limit the enhancement of the output power of the laser. Low-pass spatial filtering without focusing can surmount the drawbacks of the pin-hole filter. The low-pass spatial filters based on Rugate coating, transmitting multilayer dielectric film and reflecting multilayer dielectric film are analyzed. And their filtering performances are validated. Based on matrix transfer method, Rugate coating and multilayer dielectric film combine device structures are investigated. The feasibility of the substitution of the non-focusing spatial filter for pin-hole filter is validated experimentally. The main contents and conclusions are as follows. 1）Rugate minus filter can be designed and fabricated and methodology for the fabrication of composite thin films by pulsed direct-current magnetron sputtering with the rapidly alternating deposition is presented. The two materials are mixed by rapidly alternating deposition technology. Several rugate minus filter samples were fabricated using an automatic deposition process. The measured transmittance spectrum of a sample is in agreement with the designed. The feasibility of fabrication of Rugate thin films spatial filter is demonstrated. 2）The phase-shifted Rugate film filter is designed and the error analysis is prepared in accordance with the actual conditions. The extinction coefficient and the preparation of technical precision are discussed to achieve excellent performance for the preparation of the thin film. The internal electric field of the phase-shift Rugate film filter is calculated. 3）The experiment setup transmitting muti-layer coating cutoff filter-combination device is presented.The angular resolution of transmitting multi-layer thin-film filters with different oblique angles of incidence and period numbers, based on phase-shifted Rugate thin-film filters, Fabry-Perot ultra-narrow bandpass filters and cutoff filter-combination device, is firstly discussed and the electric field distributions of the filters are compared. Results show that the three of transmitting multi-layer thin-film filters can realize the same angular resolution, but the electric field distributions of cutoff filter-combination device is the lowest. The main studies are given to the design, fabrication and performance analysis of cutoff filter-combination device. After the transmittance spectrum curve is fitted, for Nb2O5 δ=0.1% and SiO2 δ=0.2% ，the fitted curve has a good agreement with the measurement results. Damage threshold of the films were tested and the results show that multilayer dielectric film prepared by the ion beam sputtering is higher the damage threshold. So the combination of two cutoff filters may be applied in practical applications of devices of laser systems. 4）The experiment setup reflecting muti-layer coating cutoff filter-combination device is presented. Comparing with transmission combination device, only one type reflection element is presented in optical path of reflecting combination device, and the difficulty of design and preparation is largely decreased in the same angular spectrum selectivity. In addition, by the design of coating stacks and comparing the electric field strength, reflecting combination device has higher laser-induced damage threshold(LIDT) than the transmission. Thus, those play an incredibly important role in the preparation and application of the dielectric multilayer film reflecting combination device. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15918]  |
| 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 | 章瑛. 薄膜型空间滤波器的研究[D]. 中国科学院上海光学精密机械研究所. 2015. |
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