镜像对称型达曼光栅的研究
文献类型：学位论文
| 作者 | 毕群玉 |
| 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 | 周常河 |
| 关键词 | 分束器 达曼光栅 镜像对称 理论优化 湿法刻蚀 |
| 其他题名 | Study on Reflection Symmetric Dammann Grating |
| 中文摘要 | 在光学数据处理系统，光学逻辑器件以及光学双稳态器件等众多技术领域中都需涉及到将单一的输入转化为多信号输出的问题，光学分束器件可以实现上述要求。实现光学分束器的方法很多，基于夫琅和费衍射原理设计的，由H. Dammann提出的达曼光栅因其效率高，光束分布均匀性不受入射光强分布影响等优点，成为目前最有效的分束器件之一。此后，随着对衍射效率、光斑均匀度要求的提高以及工艺水平的改善，相继提出了各种变异型的达曼光栅。本论文将镜像对称结构引入达曼光栅，设计出反转对称型达曼光栅，并对多值位相达曼光栅进行了理论设计，其主要内容如下: 1. 反转对称型达曼光栅的设计与制造。最初奇数达曼光栅的零级衍射级次光强的计算公式与其它衍射级次的计算公式形式完全不同，零级衍射光斑对位相误差极其敏感，这会影响光斑阵列的均匀度。采用周期内位相突变点镜向对称，前后半周期位相相差结构设计的反对称型达曼光栅，可使其零级衍射光斑强度仅是位相的函数，因此可消除零级谱点。相对于消除所有偶数级次的偶数达曼光栅，反转对称达曼光栅保留了各高级偶次级光斑。鉴于反转对称达曼光栅的各高级谱点光强均匀度不受位相变化的影响，可采用同一块掩模版，通过不同的刻蚀深度增加或消除零级光强而不影响其它高级光斑的均匀度。运用快速下降算法，求解出分束比从14到114的二值和多值位相反转达曼光栅的数值解，实验上设计了16的反转对称达曼光栅的模版，运用不同刻蚀深度制作出消除零级的16（光斑分布与偶数达曼光栅不同）和添加零级的17（光斑分布与奇数达曼光栅相同）光栅。更重要的是，通过将两个一维达曼光栅正交，实现了无中心光强的66二维阵列分布，这是以往的一维奇数和偶数达曼光栅通过正交所无法实现的。 2. 多位相达曼光栅的理论设计。达曼光栅的位相通常取二值，虽然这便于大规模集成电路技术加工达曼光栅，但是同时也限制了调制参数的个数，导致其衍射效率较低。增加位相调制参数虽然可以有效提高衍射效率，但是同时也增加了评价函数的复杂度，加大优化难度。计算出分束比高达164二值位相达曼光栅的快速下降算法对于分束比大于17的多值位相达曼光栅搜索不出合适的解（均匀度小于10-4）。本文采用令周期内位相突变点关于中点镜向对称，令相等正负衍射级次相等的方法简化评价函数，减小理论设计的难度，并成功求解出分束比从13到115的多位相达曼光栅数值解（均匀度小于10-4）。 |
| 英文摘要 | In many technical fields, such as optical data processing systems, optical logic gates, optically bistable elements and so on, involve the transformation of an input into several outputs and optical array generators can achieve this transformation. Among numerous methods to obtain array generation, Dammann gratings, named after the inventor H. Dammann, are based on Fraunhofer diffraction and are one kind of the most effective elements to generate array for high diffraction efficiency with good uniformity. Subsequently, various Damamnn gratings are proposed for enhencing uniformity and the improvement of the fabrication technique. This dissertation concentrates on the application of symmetry in the design of Dammann gratings for controlling of the zero order’s intensity and higher order’s intensities. Numerical solutions of multilevel Dammann gratings are also given. The main contents are as follows: 1. The design and fabrication of the inverse symmetric Dammann gratings. The zero order’s intensity is more sensitive to the phase error than the higher orders’. A configuration that transition points are reflection symmetric about the midpoint with phase offset in one period is proposed. The intensity of the zero order becomes the function of the phases and can be eliminated. Compared with the even-numbered Dammann gratings, inverse symmetric Dammann gratings retain the higher even orders. As there is no effect on uniformity as a result of phase transformation, adding or eliminating the zero order intensity is possible. The steepest descent algorithm is adopted to search the numerical solutions of binary and multilevel phase symmetric inverse Dammann grating with splitting ratio from 14 to 114. Two gratings, one is a 16 grating without the zero order and the other is a 17 grating with the zero order, are fabricated using the same mask with two different etching depths. Furthermore, an 66 array without the central zero order can be achieved by employing dual crossed one-dimensional symmetric Dammann gratings, which can not be realized by crossing two one-dimensional odd-numbered or even-numbered Dammann gratings. 2. Optimization of multilevel Dammann gratings. Dammann gratings are normally designed as binary phase, which usually fabricated with integrated circuit technique, but that confines the modulation parameters and leads to the low diffraction efficiency. Although adding phase modulation is an effective way to improve diffraction efficiency, it also makes the cost function more difficult to be optimized for more modulation parameters. For the steepest descent algorithm, which have searched the numerical solutions of binary Dammann gratings with splitting ratio up to 164 successfully, no satisfied numerical solutions, whose uniformity is better than 10-4, are obtained when the splitting ratio is larger than 17. Therefore, a configuration whose transition points are symmetric about the middle point in order to ensure the equivalence of intensities of matching negative- and positive-order pairs is adopted to reduce the complexity of optimization and the solutions with splitting ratio from 13 to 115 are obtained. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16393]  |
| 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 | 毕群玉. 镜像对称型达曼光栅的研究[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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