| 题名 | 渐变折射率薄膜的设计与制备 |
| 作者 | 张俊超 |
| 学位类别 | 博士 |
| 答辩日期 | 2012 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 贺洪波 |
| 关键词 | 渐变折射率 减反膜 Rugate滤光片 空间滤波器 |
| 其他题名 | Design and fabrication of graded index coatings |
| 中文摘要 | 渐变折射率薄膜的显著特点是沿膜层表面法线方向折射率连续变化，平行于膜面方向上折射率保持不变。这种膜系以其折射率渐变的特点，具备诸多常规均匀薄膜所无法实现的光学性能及力学特性。本文针对渐变折射率薄膜的主要应用膜系—渐变折射率减反膜和Rugate滤光片，对其设计方法和实验制备技术进行了系统研究。具体工作如下： 通过令薄膜对偏振光的有效折射率轮廓满足五次方形式的方法实现了倾斜入射条件下偏振光减反膜的设计。应用遗传算法优化渐变折射率轮廓，实现了自然光入射条件下宽角谱宽光谱渐变折射率减反膜的优化设计，并分析了离散情况下薄膜包含台阶数对减反效果的影响。利用倾斜入射沉积技术，制备了不同沉积角度和基片旋转速度下的SiO2薄膜，分析了其光学特性和微观结构的变化规律，实现了折射率仅为1.1的薄膜材料制备。采用单一SiO2膜料，利用倾斜沉积技术制备了双台阶减反膜样品。实验过程中，运用对称沉积的方法有效减小了此技术在制备薄膜时厚度的非均匀性问题。样品在光谱(400nm-800nm)和角谱(10°-50°)范围内平均反射率仅为0.88%，与设计结果吻合较好。 通过调制折射率轮廓正弦周期大小的方式，拓宽了Rugate滤光片的光谱反射带。分析了周期分布对光谱反射带的影响。通过在周期渐变结构两端增加等正弦周期Rugate切趾层的方法，实现了反射带陡度的提高和边带波纹的压缩。结合Rugate结构和减反膜实现了光谱通带具有高透射特性的滤光片设计。基于磁控溅射镀膜装置，提出了一种通过基片快速周期性地扫过两溅射靶材表面进而实现两种膜料混合的快速交替沉积技术。通过连续改变两靶的功率实现了混合薄膜中两种材料组分比的变化，进而实现了折射率在较大范围内连续稳定控制。分析了混合薄膜折射率和沉积速率随两靶功率的变化关系。并利用此技术制备了多种Rugate滤光片样品。制备的宽带Rugate滤光片样品的反射带半高宽达到了505nm。 分析了Rugate滤光片在空间滤波器中的应用。研究了Rugate结构对光谱及角谱选择性的影响。设计了角谱选择性带宽为毫弧度量级的空间滤波器。 |
| 英文摘要 | Graded refractive index (GRIN) coating is a layer of inhomogeneous film with gradient-index in which the refractive index varies gradually along its normal axis whereas keeps uniform in the directions parallel to the surface. Comparing with tranditional optical thin films, graded index coatings have many advantages in their optical and mechanical performances. In this thesis, the design and fabrication of graded index antireflection coatings and rugate filters are discussed. The detailed work is briefly introduced as followings: Quintic effective refractive-index profile is used to design the broadband GRIN antireflection coating (AR) for a given state of polarization at off-normal incidence. The genetic algorithm is used to optimize the refractive index profile of the wide-angle and broadband GRIN antireflection. The optimization of step-graded GRIN AR coating is also investigated in detail. The nanostructured SiO2 films were prepared by electron beam evaporation with the glancing angle deposition at different oblique angles and substrate rotation. The optical properties and structures of these films were analyzed. The minimum refractive index of 1.1 was realized in our coating system. An optimized two-layer AR coating with a simple structure was fabricated by oblique angle deposition technique using low-n SiO2 material only. The positional homogeneity was improved by depositing the film from two opposite directions. The measured average reflectance in the wavelength range of 400nm - 800nm and angular range of 10°- 50°is 0.88%, which is in agreement with the calculated results. The design and the deposition of rugate filter for broadband applications are discussed. The bandwidth is extended by increasing the rugate period continuously with depth. The width and the smoothness of the reflection band with the distribution of the periods are investigated. The improvement of the steepness of stopband edges and the suppression of the side lobes in transmittance zone are realized by adding two apodized rugate structures with fixed periods at the external broadband rugate filter interfaces. Filters that have high transmittance over the passband region of the reflectance spectrum are designed by combining rugate structures and antireflection coatings. 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. The refractive indices and deposition rates of the composite films varying with the composition of the material are studied in detail. Several rugate filter samples were fabricated using an automatic deposition process. The measured transmittance spectrum of a sample with a reflection band width of approximately 505 nm is close to that for the designed broadband rugate filter. The application of rugate structures in the spatial filters is analyzed. The spectral and angular selectivity varied with the structural parameters of rugate spatial filters are studied. A spatial filter with an angular spectrum bandwidth of mrad is designed. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15691]  |
| 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 | 张俊超. 渐变折射率薄膜的设计与制备[D]. 中国科学院上海光学精密机械研究所. 2012. |
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