基于自支撑二元亚波长光栅结构的太赫兹分束器设计

发布时间：2018-02-25 23:20

本文关键词： 二元光学严格耦合波理论亚波长光栅自支撑结构太赫兹偶数分束器遗传算法　出处：《深圳大学》2016年硕士论文　论文类型：学位论文

【摘要】：太赫兹功能器件作为太赫兹技术应用中的关键和基础,目前相关的研究主要集中在以光子晶体、表面等离子体、超颖光栅、石墨烯等复杂结构实现太赫兹的分束、滤波、偏振控制等方面,复杂的结构导致制作困难,成本较高,实际效果不理想。所以,结构简单、功能优异的太赫兹功能器件的研究极具科学意义。本文在实验室长期二元光学器件研究的基础上,将严格耦合波理论与遗传算法相结合,提出并设计了基于自支撑简单周期结构的太赫兹偶数分束器,实现高衍射效率、高均匀性、高零级抑制效果,同时简单结构的应用极大地降低了制作难度和成本,可使太赫兹功能器件进一步实用化。目前国内外基于自支撑简单周期结构的二元光栅实现太赫兹偶数分束的研究未见报道。本文的主要研究内容如下:1.以严格耦合波理论为基础,建立平面波入射自支撑简单周期结构条件下太赫兹分束器各级衍射效率与自支撑结构参数(光栅周期d、光栅占空比f、光栅深度h、光栅材料折射率n)的映射关系;为自支撑亚波长光栅太赫兹分束器的衍射效率和均匀性设置恰当的评价函数,结合遗传优化算法,根据优化结果不断调整评价函数各项权重因子,给出合适的权重因子。2.综合运用严格耦合波理论与遗传算法,基于自支撑简单周期结构的二元光栅,设计了分束数为二、四、六的三款偶数硅基太赫兹分束器。最佳分束效果为:高阶总衍射效率能够达到99.14%,零级透射率抑制在0.188%以内,均匀性误差控制在6.16×10-16以内。3.分析了光栅结构参数的制作误差和入射光参数的偏差对自支撑亚波长光栅偶数分束器分束性能的影响,给出了分束器光栅结构参数和入射光参数对分束效果的影响规律,该工作对于所设计分束器的制作和测试有一定的指导意义;对所设计的分束器进行结构参数公差分析,给出了最佳制作参数,该工作可以指导自支撑亚波长光栅太赫兹偶数分束器的实际制作。4.用硅基材料制作了工作波长为118.83μm的自支撑亚波长光栅太赫兹四分束器,分析了实际制作误差的原因,并给出了相应的解决办法。本文提出并设计了基于自支撑二元简单周期结构的亚波长光栅的太赫兹偶数分束器,结合矢量分析理论与遗传优化算法设计了二、四、六三款偶数分束器,突破了传统标量方法设计的局限性,有效地抑制了零级衍射;本文所设计和制作的太赫兹偶数分束器由于结构简单、功能可扩展、制作方便,可望在未来太赫兹通讯与成像系统中获得应用。
[Abstract]:Terahertz functional devices are the key and foundation of terahertz technology application. At present, the related research mainly focuses on the realization of terahertz beam splitting and filtering with complex structures such as photonic crystal, surface plasma, superglume grating, graphene and so on. In polarization control and other aspects, the complicated structure leads to the difficulty of making, the high cost, and the actual effect is not ideal. Therefore, the structure is simple, The research of terahertz functional devices with excellent function is of great scientific significance. In this paper, strict coupled wave theory is combined with genetic algorithm on the basis of long-term binary optical device research in laboratory. A terahertz even-number beam splitter based on self-supporting simple periodic structure is proposed and designed to achieve high diffraction efficiency, high uniformity and high zero order suppression. The application of simple structure greatly reduces the fabrication difficulty and cost. It can make THz functional devices more practical. At present, there is no report on the realization of terahertz even-number beam splitting based on self-supporting simple periodic grating at home and abroad. The main contents of this paper are as follows: 1. Strictly coupled. Based on the theory of combined wave, The mapping relationship between the diffraction efficiency of terahertz beam splitter and the parameters of self-supporting structure (grating period d, grating duty cycle f, grating depth h, refractive index of grating material n) under the condition of simple periodic structure of incident plane wave is established. For the diffraction efficiency and uniformity of the self-supporting sub-wavelength grating terahertz beam splitter, the appropriate evaluation function is set up. Combined with genetic optimization algorithm, the weight factors of the evaluation function are continuously adjusted according to the optimization results. The appropriate weight factor is given. 2. Combining the strictly coupled wave theory and genetic algorithm, based on the binary grating with self-supporting simple periodic structure, the beam splitting number is designed to be two and four. The best beam splitting effect is that the total diffraction efficiency of higher order can reach 99.14 and the transmission of zero order is limited to 0.188%. The uniformity error is controlled within 6.16 脳 10 ~ (-16). 3. The effects of the fabrication error of grating structure parameters and the deviation of incident light parameters on the beam splitting performance of self-supporting sub-wavelength even number beam splitter are analyzed. The influence of beam splitter grating structure parameters and incident light parameters on beam splitting effect is given. The work is of guiding significance for the fabrication and testing of the designed beam splitter, and the structural parameter tolerance analysis of the designed beam splitter is carried out. The optimum fabrication parameters are given. This work can guide the practical fabrication of the self-supporting sub-wavelength grating terahertz even number splitter. Finally, the self-supporting sub-wavelength grating terahertz beam splitter with the working wavelength of 118.83 渭 m has been fabricated with silicon based material, and the self-supporting sub-wavelength grating terahertz beam splitter with the working wavelength of 118.83 渭 m has been fabricated. The causes of practical fabrication errors are analyzed, and the corresponding solutions are given. In this paper, a terahertz even number beam splitter for subwavelength grating based on self-supporting binary simple periodic structure is proposed and designed. Combined with vector analysis theory and genetic optimization algorithm, two, four and six even-number beam splitters are designed, which break through the limitation of traditional scalar method and effectively suppress zero-order diffraction. The terahertz even-number beam splitter designed and fabricated in this paper is expected to be used in terahertz communication and imaging systems in the future due to its simple structure, extensible function and convenient fabrication.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN25

【相似文献】