基于纳米天线阵列的表面等离激元定向激发和聚焦

发布时间：2018-03-08 08:27

本文选题：表面等离激元　切入点：定向激发　出处：《哈尔滨工业大学》2016年博士论文　论文类型：学位论文

【摘要】：表面等离激元(Surface Plasmon Polaritons,SPP)是金属表面自由电子与外部电磁场相互作用形成的一种表面电磁模式。由于SPP具有局部场增强效应,并能将激发的电磁场能量局域在突破衍射极限的亚波长尺度内,因而它在生物、化学传感,光伏设备,光刻,集成光学元器件以及非线性光学等领域具有重要的应用前景。在微纳米尺度下实现SPP的可控激发对SPP的各类应用具有非常重要的意义。另外,利用等离激元透镜对SPP进行聚焦可产生等离激元涡旋场和实现亚波长局域等,在光镊、光刻和针尖增强拉曼光谱技术等领域具有重要的应用。本论文主要研究基于纳米天线阵列的SPP可调定向激发,等离激元涡旋场的激发和SPP的中心对称聚焦,并提出一种新颖的微型化光波偏振态检测方案。设计了刻蚀在金薄膜上的V型纳米天线阵列,理论研究和数值模拟结果表明该阵列可用于SPP的可调定向激发。设计的V型纳米天线存在两种对称性相反的共振模式,它们激发的SPP分别具有对称和反对称的场分布。任意偏振态入射时结构?x方向激发的SPP为具有这两种对称性的SPP相互干涉叠加的结果,因此?x方向激发的SPP随入射光偏振态改变而变化。在圆偏振光和椭圆偏振光入射下还实现了?x方向SPP的单向激发。进一步优化结构参数,还实现了线偏振光入射下SPP的可调定向激发和单向激发。基于刻蚀在金膜上按阿基米德螺旋线排列的纳米狭缝构造了等离激元透镜,理论分析和数值研究了它在线偏振光入射下产生等离激元涡旋场的特性。研究结果表明,该等离激元透镜在特定偏振方向的线偏振光入射下,沿不同方位角激发的SPP具有相同的振幅但相位随方位角变化。这些SPP传播到等离激元透镜中心时相互干涉,形成光强中心对称分布相位随方位角变化的等离激元涡旋场。等离激元涡旋场的阶数为n?1,其中n为等离激元透镜内侧阿基米德螺旋线最大和最小半径之差与SPP波长的比值,+1或-1由线偏振入射光偏振方向和等离激元透镜中纳米狭缝的取向决定。此外,将等离激元透镜中的阿基米德螺旋线分段,在等离激元透镜具有较小尺寸的情况下,可以产生高阶的等离激元涡旋场,其阶数为m?n?1,其中m为阿基米德螺旋线的段数。提出以矩形孔为基本单元,按阿基米德螺旋线排列而成的等离激元透镜,研究它在不同偏振光入射下的SPP聚焦特性。理论和数值研究结果表明该等离激元透镜能在任意偏振光入射下实现SPP的中心对称聚焦,其内部的场分布始终为零阶贝塞尔函数分布。数值模拟得到的焦斑的尺寸约为0.35个波长。当线偏振光入射时,等离激元透镜内的光强分布与线偏振态的偏振方向无关。当椭圆偏振光入射时,等离激元透镜内的光强分布与椭圆偏振态的倾角无关,但会随椭圆偏振态的椭圆度改变而变化。特别的,当入射光为右旋圆偏振光时焦点处的光强达到最大值,是线偏振光入射时的两倍;当入射光为左旋圆偏振光时焦点处的光强达到最小值几乎为零。研究了两个纳米狭缝排列的等离激元透镜的SPP聚焦特性,并基于这两个等离激元透镜提出了一种新颖的微型化检测入射光偏振态的方案。理论和数值研究发现,这两个等离激元透镜在任意偏振态入射时均能将激发的SPP中心对称的聚焦到它们的中心,形成零阶贝塞尔函数场分布。其次,它们内部光强分布的振幅与入射光偏振态相关。利用这一特性,可只通过测量这两个等离激元透镜内的四个光强值,实现入射光全部斯托克斯参量的检测即偏振态的检测,而每个等离激元透镜的尺寸只有大约6μm。
[Abstract]:The surface plasmon (Surface Plasmon, Polaritons, SPP) is a kind of surface electromagnetic modes of metal surface free electrons and external electromagnetic fields interact to form. Because SPP has the local field enhancement effect, and can be electromagnetic energy localized excitation in Ya Bo long scale beyond the diffraction limit, so it in biological, chemical sensing. Photovoltaic devices, lithography, has important application prospect of integrated optical components and nonlinear optics and other fields. The realization of SPP control in the micro nano scale has a very important significance to inspire all kinds of application of SPP. In addition, the use of plasmonic lens for SPP focusing can produce plasmon subwavelength and vortex field local, in optical tweezers, lithography and tip enhanced has important applications of Raman spectroscopy technology. This paper mainly studies the nano antenna array SPP based on tunable directional excitation, etc The center of symmetry focusing polariton vortex field excitation and SPP, and proposes a novel miniaturized polarization detection scheme. The V type nano antenna array in etching a thin gold film on the design, theoretical analysis and numerical simulation results show that the array can be used for SPP adjustable directional excitation. There are two kinds of symmetry on the contrary the resonance mode of the V type nano antenna design, they excited SPP respectively with symmetric and antisymmetric field distribution. The incident polarization direction of the excitation structure? X SPP with the two symmetry SPP interference superposition results, therefore? X direction excitation of SPP varies with the incident light the polarization change in circularly polarized light and elliptically polarized light incident is also realized? One-way X direction of SPP excitation. And further optimize the structure parameters, also achieved a linearly polarized light SPP tunable directional excitation and unidirectional excitation based on etching. In the gold film by nano slit Archimedes helix arrangement structure plasmonic lens, theoretical analysis and Numerical Study on the polarization of the incident light under its online from the properties of polaritons vortices. The results show that the plasmonic lens in specific polarization direction line polarized light incident, along different azimuth excited SPP has the same amplitude but the phase variation with azimuth. These SPP spread to the plasmonic lens at the center of the mutual interference of the formation of isocandela center symmetric distribution phase variation with azimuth plasmonic vortices. The order of polariton vortices is 1, the ratio of N? Where n is the biggest plasmonic lens inside the Archimedes spiral line and the minimum radius difference with the wavelength of SPP, +1 or -1 by linear polarization and the polarization direction of the incident light from the orientation of nano slit polaritons in the lens. In addition, the plasmonic lens in the Archimedes spiral line segments in the plasmonic lens with the small size of the case, can produce high order plasmon vortex field and its order is m? N? 1, where m is the number of Archimedes spiral line. The rectangular hole as the basic unit, the plasmonic lens etc. and according to the Archimedes spiral arrangement, study it under different polarization of the incident light SPP focusing characteristics. Theoretical and numerical results show that the plasmonic lens can achieve symmetrical focusing SPP in arbitrary polarized incident field, its internal distribution is always zero order Bessel function distribution. Numerical simulation of the focal spot the size is about 0.35 wavelengths. When linearly polarized light incident from the polarization direction of light intensity distribution in the lens and excitation linear polarization. When the elliptically polarized light incident angle from the light intensity distribution in the polariton lens and elliptical polarization Nothing, but will change with the ellipticity of the elliptical polarization state changes. In particular, when the incident light is right circularly polarized intensity at the focus reaches the maximum value is two times the line polarized light; when the incident light is left circularly polarized light intensity at the focus reaches the minimum value is almost nil. Two nano slit arranged plasmonic lens SPP focusing characteristics, and based on these two plasmonic lens presents a novel miniaturized detection of the polarization state of the incident light scheme. Theoretical and numerical study found that the two plasmonic lens in arbitrary polarization state of the incident were can SPP will focus on the central symmetry excited by their center, the formation of zero order Bessel function distribution. Secondly, their internal intensity distribution of amplitude and polarization state of incident light. Using this characteristic, only by measuring the two plasmon lens in the Four light intensity values, the detection of all the Stokes parameters of the incident light, that is, the detection of the polarization state, and the size of each lensing lens is only about 6 m.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O485;TN820.15

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