深刻蚀石英光栅中的模式方法
文献类型：学位论文
| 作者 | 吕鹏 |
| 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 | 周常河 |
| 关键词 | 熔融石英深刻蚀光栅 波长无关分束光栅 宽带光栅 归一化简化模式方法 法布里－珀罗干涉模式方法 |
| 其他题名 | Modal Method in Deep-Etched Fused-Silica Gratings |
| 中文摘要 | 光栅是最典型的周期性光学器件之一，在现代光学系统中得到了广泛的应用，例如光谱测量系统和啁啾脉冲压缩系统中。自两个多世纪前光栅诞生以来，光栅理论和制作技术得到持续的发展。随着近年来微电子刻蚀工艺的成熟和在光栅制作方面的应用，密度更高、结构更为复杂的光栅的设计理论和制作技术继续为研究者所关注。基于目前高密度光栅的研究现状，本硕士论文主要针对熔融石英高密度深刻蚀光栅，介绍了以下几方面的研究工作： 1) 基于归一化简化模式方法，给出了熔融石英分束光栅的波长无关归一化结构参数，并分析了熔融石英中实现波长无关归一化设计的原因。一般认为，光栅模式方法可用于指导特定波长下的光栅设计，而严格耦合波分析只能得到特定波长下光栅各级衍射效率的数值解。将光栅参数对入射波长归一化，并在简化模式方法中定义光栅归一化结构参数为：光栅周期与入射波长的比值，沟槽深度与光栅周期的比值。由此可知在低色散材料中可能得到波长无关的光栅归一化结构参数。区别于宽带光栅，这里的波长无关指光栅归一化结构参数的波长无关特性。结合严格耦合波分析和模拟退火优化算法，我们在紫外到近红外波段，分别给出了熔融石英波长无关偏振分束光栅和偏振无关分束光栅的归一化优化参数。计算光栅区内传播模有效折射率的变化，进一步分析了熔融石英的低色散特性实现波长无关归一化设计的原因。所设计的光栅归一化优化参数可直接用作特定波长下光栅参数的优化初始值，极大地减少了光栅设计中的重复运算，提高了光栅设计的效率，对指导分束光栅设计（尤其在低色散材料中）有重要的实际意义[相关论文已提交到Opt. Commun.，目前正在修改]。 2) 提出了熔融石英宽带光栅中的法布里－珀罗干涉模式方法，并分析了所设计的宽带飞秒脉冲压缩光栅的衍射过程。简化模式方法中光栅传播模在界面处的反射被忽略，Clausnitzer等首先在设计1064纳米波长透射效率为100%的浸入式(buried/immersed)光栅时引入了传播模法布里－珀罗干涉的概念，但并没有对一般的(非浸入式的)宽带光栅结构中的衍射过程进行分析。在我们给出的法布里－珀罗干涉模式方法中，采用等效近似的方法，引入了光栅传播模在界面处的反射和透射菲涅耳系数，并考虑了光栅传播模在光栅区内的多次往返传播。相比简化模式方法，法布里－珀罗干涉模式方法整体计算结果低于严格耦合波，中心波长附近计算结果低于简化模式方法，但整体上更符合严格耦合波的计算结果，因而更能反映宽带光栅内部衍射的物理过程，结论显示传播模的法布里－珀罗干涉效应能有效的解释光栅的宽带衍射特性。法布里－珀罗干涉模式方法不仅提供了一条利用经典模式方法计算光栅衍射效率的便捷之道，而且经过进一步完善后有可能用于分析高折射介质光栅和多层膜介质光栅中的衍射过程。 在使用法布里－珀罗干涉模式方法分析宽带光栅的衍射过程之前，基于严格耦合波分析，我们采用光栅在一定带宽内衍射效率平均值和标准差来衡量光栅的衍射特性。根据Kogelnik耦合波理论选择入射光偏振方向，并结合模拟退火优化算法进行光栅优化设计。采用最简单的单层结构，分别设计了TE偏振宽带飞秒脉冲压缩光栅和TM偏振窄带高效率飞秒脉冲压缩光栅。光栅占空比为0.5时，在800纳米中心波长对应的利特罗角入射下，所设计的TE偏振宽带飞秒脉冲压缩光栅－1级衍射效率在入射波长为735-861纳米时高于93.9%；所设计的TM偏振窄带高效率飞秒脉冲压缩光栅在780-820纳米带宽内－1级衍射次效率高于97.2%，最高衍射效率在中心波长处达到97.96%。 3) 采用全息干涉记录、反应等离子耦合刻蚀方法，我们制作了所设计的宽带飞秒脉冲压缩光栅，相关的实验工作还在进行中。在实验中积累了丰富的光栅制作经验，并对其中部分细节进行了改进，本论文将对此进行总结，并分析实际制作结果，对于继续完善光栅制作工艺有重要的实际意义。 本硕士论文，主要研究了熔融石英高密度深刻蚀光栅归一化简化模式方法，提出了考虑传播模法布里－珀罗干涉效应的简化模式方法，并对其制作工艺进行了研究。这些工作有利于了解熔融石英深刻蚀光栅的衍射特性，指导光栅设计并推进其实际应用。 |
| 英文摘要 | Grating is one of the most typical periodic optical devices, which has been widely used in modern optical systems, such as spectrum measurement and chirped pulse compression systems. Since invented two centuries before, theories and fabrication technologies of gratings have been developed continuously. In recent years, with the progress of microelectronic etching technology and its applications in grating fabrication, theories and fabrication technologies of gratings with higher densities and more complex structures are still the focus of the current research. My research is mainly focused on deep-etched fused-silica gratings, including the following aspects in this Master’s dissertation: 1) Based on the unified simplified modal method, we have designed wavelength-independent beam splitter gratings in fused-silica, and analyzed the wavelength-independent grating structures in fused-silica. It is widely-accepted experience that, the grating modal method can be used to design grating under a particular wavelength, and the rigorous coupled-wave analysis (RCWA) can be used to produce the numerical solution at a given wavelength as well. Unified grating parameters in simplified modal method are defined as the ratio of incident wavelength to grating period, and the ratio of groove depth to grating period. We can learn that it is possible to acquire wavelength-independent unified grating structures in low dispersion materials. By using RCWA and simulated annealing (SA) algorithm, we have designed a wavelength-independent polarizing beam splitter and a wavelength-independent polarization-independent beam splitter in fused-silica from ultraviolet to near infrared, respectively. By calculating effective indices of propagating grating modes inside the grating area, we have analyzed the wavelength-independent grating structures in fused-silica. The optimum unified grating parameters can be directly used as initial values for grating parameter optimization, which will greatly decrease the calculation during grating design and improve the design efficiency. This unified simplified modal method will be used for practical applications in beam splitter grating design, especially in low dispersion materials. [This work has been submitted to Opt. Commun., in revision] 2) We have provided a Fabry-Perot effect incorporated modal method (FPMM) for wideband gratings in fused-silica, which has been used to analyze the diffraction process of designed wideband grating for femtosecond pulse compression. As reflection of propagating grating modes at interfaces inside the grating area has been neglected in simplified modal method, Clausnitzer et al firstly consider Fabry-Perot effect of propagating grating modes in simplified modal method, for designing a buried transmission grating with 100% -1st diffraction efficiency at the incident wavelength of 1064 nm, while they have not analyzed the diffraction processes of binary wideband gratings. We have introduced the equivalent Fresnell coefficients of propagating grating modes in FPMM, and it takes the Fabry-Perot effect of propagating grating modes into account. Compared with simplified modal method, the calculation result of FPMM is lower than RCWA overall, and lower than simplified modal method around the central wavelength, while it agrees better with RCWA generally. FPMM provides a more practical physical image of the diffraction process inside the grating area. Fabry-Perot effect of propagating grating modes is proven to be effective for explanation of broadband diffraction efficiency of gratings. In addition of diffraction process analysis, FPMM also provides a direct way of calculating the diffraction efficiency of gratings based on modal method, which is possible to be used in analysis of diffraction processes of more complex grating structures after further improvements, such as high index gratings and multi-layer all-dielectric gratings. Before analyzing the diffraction processes of wideband gratings by FPMM, based on RCWA, we use mean and standard deviation of diffraction efficiency to evaluate the diffraction performance of gratings over a given bandwidth. With Kogelnik theory and SA algorithm, we have designed a TE polarization wideband grating and a TM polarization narrowband high-efficiency grating for femtosecond pulse compression, with the simplest single layer binary structure in fused-silica. In our design, the grating duty cycle is fixed at 0.5, and it is illuminated under the Littorw mounting of the central wavelength of 800 nm. The -1st diffraction efficiency of the wideband grating is above 93.9% within the wavelength range of 735-861 nm; the -1st diffraction efficiency of the narrowband high-efficiency grating is above 97.2% inside a 40 nm bandwidth from 780 nm to 820 nm, with the highest diffraction efficiency of 97.96%. 3) By using holographic recording and inductively coupled plasmon etching technologies, we have fabricated the TE polarization wideband grating for femtosecond pulse compression, and the experimental work is still in progress. We have accumulated experience during experiments, and made some improvements to experimental details, which are important for practical applications in future grating fabrication. This Master’s dissertation mainly investigates unified simplified modal method of high-density deep-etched fused-silica gratings. The Fabry-Perot effect incorporated modal method is introduced, and some research on fabrication technologies of high-density deep-etched fused-silica gratings is carried out. Research in this dissertation contributes greatly to grating design and practical applications of high-density deep-etched fused-silica gratings. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16684]  |
| 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 | 吕鹏. 深刻蚀石英光栅中的模式方法[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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