基于表面等离激元的光器件设计及研究

发布时间：2018-01-20 13:50

本文关键词： 表面等离子激元纳米聚焦类似阶梯型结构相干相长　出处：《北京邮电大学》2015年硕士论文　论文类型：学位论文

【摘要】：表面等离子激元(Surface Plasmon Polaritons, SPPs)是光波与金属表面自由电子相互作用而形成的一种特殊的电磁波形式,它能够很好的束缚于金属表面,离开金属表面则会指数型衰减。并且SPPs有着突破光的衍射极限的特性,所以对于光学器件微型化有着极大的潜能。并且在亚波长的金属结构中,SPPs表现出了特殊的光学传输特性,这个特性可以大大增加传输光的效率,对于实现紧凑的纳米聚焦器件有着重要的作用。这些纳米聚焦器件主要应用于纳米光束整形,集成光学,数据储存以及近场成像等领域。因此各种各样基于SPPs的金属结构被设计出来为了实现纳米聚焦,以及通过不断的改进结构来增强聚焦强度。本文首先针对Van Duong Ta在2011年提出的杂化波导结构,通过增加空气柱、介质膜等方式进行了结构参数的优化。使得传播距离从628μ m增加到1514μ m,同时光斑大小从2.17e-6μm减小到1.2e-6μ m,实现了长传播距离的高束缚SPPs波导结构。然后基于对纳米聚焦器件的深入调研提出一种新型的纳米聚焦器件,先前的研究者提出的纳米聚焦结构都是拥有很多水平排列的子结构,而本研究所提出的结构是对不同的微米缝在垂直方向上进行排列,所以水平尺寸只有2μ m,远小于其他纳米聚焦器件的尺寸,更加有利于器件集成。这种阶梯型结构实现高效聚焦主要基于以下几个原理：在宽缝中成功的多模干涉作用,传输光与散射的SPPs发生相干相长作用,以及高折射率介质膜的FP腔效应。最终这种阶梯型单一微米缝结构实现了I=5.15的高聚焦强度和FWHM=300nm(λ/2的光斑大小的聚焦。进而针对上述阶梯型聚焦结构进行了参数优化,通过对每层金膜厚度以及微米缝宽度的修改,在500nm厚度的金膜上实现了三维纳米聚焦透镜。并且利用聚焦离子束(FIB)在500nm厚度的金膜上成功刻蚀了实验样品。最后设计了一种阶梯型单一纳米缝结构,它能够在焦距600nm处实现聚焦。当入射波长为830nm时候,通过数值仿真得到了光斑大小为FWHM=423nm的二维聚焦,以及光斑大小为FWHMX=426nm,FWHMy=690nm的三维透镜聚焦,并且在实验上成功观测到聚焦现象。总的来说本文理论提出并实验验证了一种新的设计纳米聚焦器件的方法,这种方法具有灵活性,通过改变结构参数能够对不同波长进行聚焦。而所提出的聚焦器件利用垂直排列子结构,有着更小的水平尺寸,利于器件的集成。
[Abstract]:Surface Plasmon Polaritons. SPPsis a special form of electromagnetic wave which is formed by the interaction of light wave and free electron on metal surface. It can bind to metal surface very well. Without metal surface, exponential decay occurs. Moreover, SPPs has the characteristics of breaking through the diffraction limit of light, so it has great potential for miniaturization of optical devices, and in subwavelength metal structures. SPPs shows special optical transmission characteristics, which can greatly improve the efficiency of optical transmission. These nano-focusing devices are mainly used in the shaping of nano-beam and integrated optics. Therefore, various metal structures based on SPPs have been designed to achieve nano-focusing and to enhance the focusing intensity through continuous improvement of the structure. In this paper, firstly, the hybrid waveguide structure proposed by Van Duong Ta in 2011 is introduced by adding air column. The structure parameters were optimized by the dielectric film, the propagation distance was increased from 628 渭 m to 1514 渭 m, and the spot size was reduced from 2.17e-6 渭 m to 1.2e-6 渭 m. A high bound SPPs waveguide structure with long propagation distance is realized. Then, based on the in-depth investigation of nano-focusing devices, a new type of nano-focusing devices is proposed. The nanofocusing structures proposed by previous researchers are all substructures with many horizontal arrangement. The structure proposed in this paper is arranged in vertical direction for different micrometers, so the horizontal size is only 2 渭 m, which is much smaller than that of other nano-focusing devices. This kind of step structure is mainly based on the following principles: successful multimode interference in wide slit and coherent interaction between transmitted light and scattered SPPs. And the FP cavity effect of high refractive index dielectric film. Finally, the single micrometer slit structure of this kind of ladder can achieve the high focusing intensity of I _ (5.15) and the focus of FWHM _ (300) nm (位 / 2). Then the parameters of the step focusing structure are optimized by modifying the thickness of each layer of gold film and the width of micrometer slot. Three-dimensional nanocrystalline focusing lens was realized on the gold film of 500nm thickness, and the experimental samples were successfully etched on the gold film with the thickness of 500nm by using focused ion beam beam (FIB). Finally, a single ladder structure is designed, which can focus at 600nm focal length, when the incident wavelength is 830nm. By numerical simulation, two-dimensional focusing with FWHM=423nm size and 3D lens focusing with FWHMXX 426nm FWHMyMY 690nm were obtained. And the focusing phenomenon is observed successfully in the experiment. In general, a new method for designing nano-focusing devices is proposed and experimentally verified in this paper. This method is flexible. By changing the structure parameters, different wavelengths can be focused. The proposed focusing device uses perpendicular substructures and has a smaller horizontal size, which is conducive to the integration of the devices.
【学位授予单位】：北京邮电大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN25

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