几种周期性亚波长结构的光学特性及其器件设计

发布时间：2018-01-10 16:25

本文关键词：几种周期性亚波长结构的光学特性及其器件设计　出处：《江苏大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着激光加工技术的不断进步和成熟,人们对材料的加工技术已经可以达到纳米尺度的精度。这为亚波长结构光学性质的研究提供了条件,而亚波长结构也因为其独特的光学特性正吸引了越来越多的关注。本文首先介绍了亚波长金属结构及亚波长介质结构的研究进展,并讨论了表面等离子激元的特性。接着,本文讨论了二维周期性纳米金属圆柱结构的近场光学特性,讨论了结构参数对其近场暗中空模式的影响,并结合范德瓦尔斯势及自发辐射来讨论原子囚禁的可能性。之后,本文提出了一种基于亚波长梯形介质光栅的高带宽、超高反射率的反射镜,并讨论结构参数对于反射带宽的影响。最后,提出了一种利用亚波长介质光栅实现反射聚焦的方法,并讨论了结构参数对反射镜相位的影响。在第二部分中,提出一种采用金属圆柱阵列实现二维原子光学晶格的方案,利用有限元数值模拟方法研究了表面等离子激元特性,并考虑相邻圆柱的近场耦合,得到了三维光强分布。分析了冷原子所受光学势与范德瓦尔斯势的作用,讨论了总势场分布及势阱中心位置与结构参数的依赖关系。研究发现,金属纳米圆柱形成的光学势阱可以将冷原子囚禁在四个金属纳米圆柱中间上方的长350 nm、宽350 nm、高66 nm的周期性暗中空区域内,并且可以通过改变圆柱阵列的几何参数来调整光学势阱的空间大小与相对位置,方便对原子的操纵与控制。此外,讨论了囚禁在光学势阱中原子的自发辐射、瑞利散射与拉曼散射情况,并考虑原子的冷却特性。在第三部分中,提出了一种基于亚波长梯形介质光栅的高带宽超高反射率反射镜方法。利用严格耦合波理论和有限元数值模拟方法研究了亚波长梯形介质光栅平面波入射情况下的反射特性,发现通过两种方法得到的反射率曲线吻合得非常好。通过优化结构参数,可以得到中心频率约为1550 nm处,具有345 nm宽的高反射带宽,且其反射率超过99.9%(Δλ/λ22%)。另外,通过调整结构参数,可以获得反射带宽为80 nm,对应的反射率超过99.99%的反射镜。光栅中存在的归一化电场强度近场分布的驻波模式被用来解释高反射率形成的原因。在第四部分中,提出了基于一种准周期的亚波长介质光栅的反射聚焦方案。通过有限元数值模拟,我们发现当光栅周期L=700 nm,光栅栅格宽度l1=525 nm时,光栅栅格高度的分布符合一元二次曲线,当中间层的厚度d=600 nm时,可以获得聚焦中心处强度高于周围约5倍的反射聚焦效果。研究发现反射镜的聚焦效果和反射光栅处的相位分布有着密切的关系,还讨论了光栅的结构参数对反射光栅处相位分布的影响。
[Abstract]:With the development and maturity of laser processing technology, material processing technology has been able to achieve nanoscale precision, which provides a condition for the study of optical properties of subwavelength structures. The subwavelength structure has attracted more and more attention because of its unique optical properties. Firstly, the research progress of the subwavelength metal structure and the subwavelength dielectric structure is introduced in this paper. The characteristics of surface plasma excitators are also discussed. Secondly, the near field optical properties of two dimensional periodic nanometallic cylindrical structures are discussed, and the influence of structural parameters on the near field dark space mode is discussed. The possibility of atom trapping is discussed by combining van der Waals potential and spontaneous emission. Then, a high bandwidth and ultra-high reflectivity reflector based on sub-wavelength trapezoidal dielectric grating is proposed. Finally, a reflection focusing method using subwavelength dielectric grating is proposed, and the influence of structure parameters on the mirror phase is discussed. In the second part. A scheme of realizing two-dimensional atomic optical lattice using metal cylindrical array is proposed. The surface plasmon characteristics are studied by means of finite element numerical simulation, and the near-field coupling of adjacent cylinders is considered. The effect of optical potential on cold atom and van der Waals potential is analyzed. The distribution of total potential field and the dependence of center position of potential well with structural parameters are discussed. The optical potential well formed by metal nanometers can trap cold atoms in a periodic dark hollow region of 350 nm in length, 350 nm in width and 66 nm in height above the middle of four metal nanometers. The spatial size and relative position of the optical potential well can be adjusted by changing the geometric parameters of the cylindrical array to facilitate the manipulation and control of atoms. In addition, the spontaneous emission of atoms trapped in the optical potential well is discussed. Rayleigh scattering and Raman scattering, taking into account the cooling properties of atoms. In the third part. A high bandwidth ultra-high reflectance reflector method based on subwavelength trapezoidal dielectric grating is proposed. The plane wave incidence of subwavelength trapezoidal dielectric grating is studied by using strictly coupled wave theory and finite element numerical simulation method. The reflection properties of. It is found that the reflectivity curves obtained by the two methods are in good agreement with each other. By optimizing the structural parameters, the center frequency is about 1550 nm and the high reflectance bandwidth of 345 nm is obtained. Moreover, the reflectivity is more than 99.9 (螖位 / 位 22). In addition, by adjusting the structural parameters, the reflection bandwidth of 80 nm can be obtained. A mirror with a reflectivity of more than 99.99%. The standing wave mode of the near-field distribution of normalized electric field intensity in the grating is used to explain the formation of high reflectivity. In part 4th. A reflection focusing scheme based on a quasi-periodic subwavelength dielectric grating is proposed. By finite element numerical simulation, we find that when the grating period is 700 nm. When the width of grating grid is l1 ~ 525nm, the raster height distribution accords with the quadratic curve, and when the thickness of the middle layer is 600 nm. It is found that the focusing effect of the mirror is closely related to the phase distribution of the reflection grating. The influence of the structure parameters on the phase distribution of the reflective grating is also discussed.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN25;TH74

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