基于表面等离子体MIM波导的光学谐振腔

发布时间：2018-04-07 15:39

本文选题：表面等离子体　切入点：金属-绝缘体-金属波导　出处：《湖南大学》2014年硕士论文

【摘要】：表面等离激元(SPPs),亦称表面等离子体,是入射光子与金属表面自由电子相互作用形成的非辐射电磁模式,是沿着金属-介质界面传播的消逝波,在纳米量级上具有显著的局域增强效应。利用表面等离子体的这一特殊性质,可以实现亚波长量级上的电磁波传输与调控。基于表面等离子体的纳米光子器件是实现纳米全光网络的基础,因此如何实对现纳米尺寸上表面等离子体的有效调控成为该领域研究者关注的热点。其中表面等离子体金属-绝缘体-金属(MIM)波导避免了辐射模和泄漏模的出现,可以将电磁波有效地局域在亚波长结构内,从而实现电磁波在纳米尺度上的传输。近几年来,基于MIM波导的功能器件已被设计,如光分束器、定向耦合器、布拉格反射器、滤波器等,研究者通过调节其结构参数来实现对其性能的调节。本论文中采用时域有限差分方法,针对MIM波导结构中表面等离子体在红光到近红外波段的传输特性进行了研究,并设计了几种基于MIM波导的谐振腔结构。主要工作内容以及结果如下：提出了一种新型基于MIM波导的谐振腔结构,该结构由两个波导通道与个内嵌金属条的圆盘组成。重点研究内嵌金属条几何尺寸及其旋转角度对该结构传输性能的影响。研究发现,当金属条宽度为几十纳米时该结构呈现带通滤波的性能,调节金属条的高度可以改变滤波波长,该结构会起到可调滤波的效果。当旋转该金属条,出现了一个新的谐振模式；旋转角度的大小不仅对滤波波长有影响,而且能够有效控制谐振强度。当金属条尺寸较大,宽度和高度均两百多纳米时,该结构可以让较宽波段的电磁波通过,此时的透射谱与九十度拐角波导的透射谱类似。提出了由两个MIM波导通道与一个内嵌金属条方形谐振腔组成的复合型结构。重点研究金属条几何尺寸对该结构传输性能的影响,并与上述内嵌金属条圆盘谐振腔结构的性能进行了对比,发现两种结构在功能上非常相似。当金属条宽度为几十纳米时该结构呈现带通滤波的性能,调节金属条的高度可以改变滤波波长。旋转该金属条,透射谱上出现两个透射峰,即谐振腔内有两种谐振模式,通过调节金属条旋转角度不仅能对两种模式下的滤波波长进行微调,还能够有效调整这两种模式的谐振强度。当金属条尺寸较大,宽度和高度均两百多纳米时,该结构可以让研究波段所有的电磁波都高效通过,相当于中间的内嵌金属条方形谐振腔不存在。提出了基于MIM波导的缺陷谐振环结构。重点研究缺陷的几何尺寸及位置对其传输特性的影响。模拟计算其透射谱及共振模式下的磁场分布,并与传输线模型的计算结果进行比较,以明确该结构的传输特性。结果表明,当设置缺陷时,破坏了环腔结构原有的对称性,影响原有的几种共振模式,从而出现了新颖的滤波特性；发现其滤波特性依赖于缺陷的尺寸大小,通过改变缺陷尺寸可以有效调节滤波波长,并且当缺陷尺寸设定为特定值时,有些模式间发生简并,提高结构滤波性能。此外,缺陷谐振环结构的部分谐振模式依赖于缺陷的位置,当缺陷位置不同时,通道波导与缺陷谐振环之间的耦合强度不同,对不同谐振波长下的透射率有一定的影响。此结构在不改变结构总尺寸的情况下,可调节滤波波长,实现了更宽频段的滤波,并有效调节其透射率。
[Abstract]:Surface plasmon polariton ( SPPs ) , also known as surface plasmons , is a non - radiative electromagnetic mode formed by free electron interaction between incident photons and metal surfaces .

A novel resonant cavity structure based on MIM waveguide is proposed . The structure is composed of two waveguide channels and a circular disk with embedded metal strips . The influence of the geometry size of embedded metal strip and its rotation angle on the transmission performance of the structure is studied . It is found that when the width of the metal strip is tens of nanometers , the structure exhibits band - pass filtering performance , and the height of the metal strip can change the filtering wavelength .
when the size of the metal strip is larger , the width and the height are both more than two hundred nanometers , the structure can let the electromagnetic wave of the wider wave band pass through , and the transmission spectrum of the transmission spectrum is similar to the transmission spectrum of the ninety - degree corner waveguide .

A composite structure consisting of two MIM waveguide channels and an embedded metal strip square resonant cavity is proposed . The influence of the geometry size of the metal strip on the transmission performance of the structure is studied , and compared with the performance of the embedded metal strip disk resonator structure , the structure presents band - pass filtering performance , the height of the metal strip can be adjusted to change the filter wavelength .

In this paper , the structure of defect resonant ring based on MIM waveguide is presented . The influence of geometry size and location on the transmission characteristics of MIM waveguide is studied . The distribution of magnetic field in the transmission spectrum and resonance mode is simulated . The transmission characteristics of the structure are determined . The results show that the original symmetry of the ring cavity structure is destroyed when the defect is set , and the original resonance modes are affected , so that the novel filter characteristic appears ;
In addition , the partial resonance mode of the defect resonant ring structure is dependent on the position of the defect , and when the defect position is different , the coupling strength between the channel waveguide and the defect resonant ring is different , and the filter wavelength can be adjusted when the total size of the structure is not changed , and the filtering of the wider frequency band is realized , and the transmittance thereof is effectively adjusted .

【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN814

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