【作者】 陈宗强；

【导师】 孙骞；

【作者基本信息】 南开大学 ， 光学， 2013， 博士

【摘要】 纳米光子学通常是指研究结构在亚微米尺度(特别在小于100nm尺度)下,光子与物质或者器件相互作用的科学。表面等离激元(Surface plasmon polaritons, SPPs)是在介电常数符号相反的两种介质面(通常用金属与绝缘体)上存在的一种电磁表面波的模式,可以打破衍射极限的限制。在适当的金属与介质组成的光波导结构中,光可以被束缚在亚波长的尺度之下。因此,利用金属与介电界面上的表面等离基元可以制作高度集成的纳米器件。目前,对表面等离激元的研究已经被称为表面等离子体学(Plasmonics),是当前纳米光子学的主要分支之一。金属-绝缘体-金属(metal-insulator-metal, MIM)结构是一种典型的表面等离激元波导,利用这种波导结构的特性,人们已经在理论或实验中设计了多种表面等离激元光学器件。本论文针对纳米光子学器件中的多功能全光逻辑门,光学传感器,以及滤波器开展研究工作。第一章概述性地介绍了表面等离激元。重点讨论了金属-绝缘体(metal-insulator, MI)界面与多层膜结构的表面等离激元的特性与激发方式,表面等离激元的应用特别是在MIM结构中的纳米光子学器件的应用,纳米光子学器件设计中常用的数值算法以及在数值计算中常用到的色散介质的模型。第二章我们使用了时域有限差分法(Finite-Different Time-Domain method, FDTD)研究了多层膜结构中的多功能全光逻辑门。理论与数值计算表明,通过控制双金属纳米间隙波导的耦合距离与三金属纳米间隙波导的耦合距离,可以在一个多层膜结构中同时集成AND逻辑操作、OR逻辑操作、NOT逻辑操作以及XOR逻辑操作。我们给出了双金属纳米间隙波导与三金属纳米间隙波导的耦合方程以及相应的本征模式,并且利用矩阵的形式把数值求解出的本征模式代入到耦合方程,从而得出在不同的输入配置下不同输出端口的光强。结果显示：在多功能全光逻辑门中,AND, OR, XOR和NOT逻辑操作的消光比分别为4.1dB,11.1dB,18.0dB和18.7dB。第三章我们使用有限元法(Finite Element method, FEM)研究了矩形谐振腔中的不同的共振模式。利用MIM波导激发出金属矩形谐振腔中的窄带共振模式与宽带共振模式,通过窄带共振模式与宽带共振模式的干涉,可以形成Fano共振。我们讨论了矩形腔的尺寸与共振波长的关系,通过调控窄带共振模式与宽带共振模式共振波长的相对位置,得到了不同形状的非对称的Fano透射谱线。我们利用这种非对称谱线特有性质,设计出了纳米光学传感器。结果表明：这种折射率传感器灵敏度为530nm/RIU, FOM (figure of merit)值为650。值得一提的是,与其它一些实现非对称结构实现Fano共振不同,我们的结构是对称的。第四章我们研究了在MIM波导中级联纳米圆盘结构的透射特性。通过控制级联纳米圆盘中不同的圆盘的半径,在通信波长1550nm处,实现了高透过率(约90%)、高Q值(约为60)滤波特性。分析这种滤波特性的本征模式可知,与单一纳米圆盘共振的模式不同,级联纳米圆盘结构中产生了联合共振模式。这种联合共振模式保证了滤波器的高透过率与高Q值。我们还分析了级联纳米圆盘的结构参数对滤波器的输出波长以及Q值的影响。结果显示：该滤波器的输出波长与圆盘的半径成线性关系,其Q值受到R1/D的调控。第五章我们对本论文进行了总结,并就下一步纳米光子学器件的研究工作进行了展望。更多还原

【Abstract】 Nanophotonics is a newly developing and exciting field. By nanophotonics one usually refers to the science and devices involving structures with sub-micron dimensions (specifically less than100nm) and which are interacting with photons. Surface plasmon polaritons (SPPs) are electromagnetic excitations propagating at the interface between a dielectric and a conductor, evanescently confined in the perpendicular direction. Currently, in the proper consisting of metal and dielectric waveguide structure, electromagnetic fields is confined over dimensions on subwavelength can be used to produce highly integrated nanodevices. SPPs is now known as Plasmonics which is a major part of the fascinating field of nanophotonics. Metal-insulator-metal (MIM) waveguide is a typical SPPs waveguide. By using characteristics of MIM waveguide, numerous plasmonics device have been numerically and/or experimentally demonstrated, such as splitters, wavelength demultiplexer, Mach-Zennder interferometers, all-optical switches, nanofocusing, networks, and so on. This thesis focuses on nanophotonics devices of multifunctional all-optical logic gates, sensor, and filter in MIM structure.The first chapter introduces the characteristics of the multilayer film structure surface plasmon polaritons, and then describes the application of nanophotonics based on SPPs, especially a variety of nanophotonics devices with the MIM structure, and finally introduced numerical methods in the design of nanophotonics devices and the model of dispersive media in the numerical calculation.In the second chapter, we use the FDTD method to study multifunctional all-optical logic gates in the multilayer film structure. Theory and numerical calculations show that by tuning the coupling distance of metal gap waveguides, one can integrated AND, OR, NOT, and XOR logic gates in a multi-layer film structure. The coupled equations and the corresponding eigenmode was given, and so as the light intensity of each of the different output ports. In this work, the light intensity of each of the different output ports is strongly dependent on the thickness of the metal in the metal nano-gap waveguide arrays, which is due to the thickness of the metal film has a tremendous impact on the coupling coefficient. The extinction ratios of AND, OR, XOR, and NOT operation in multifunctional all-optical logic gates are4.1dB,11.1dB,18.0dB, and18.7dB, respectively.In the third chapter, a novel symmetric plasmonic structure which consists of an MIM waveguide and a rectangular cavity is proposed to investigate the Fano resonance performance by adjusting the size of the structure. The Fano resonance originates from the interference between a local quadrupolar and a broad spectral line in the rectangular cavity. It is realized that tuning the Fano profile by changing the size of the rectangular cavity. The nanostructure is expected to work as an excellent plasmonic sensor with a high sensitivity of about530nm/RIU and a figure of merit (FOM) of about650.In the fourth chapter, a plasmonic waveguide filter based on three cascaded nanodisks is proposed. By tuning the radius of cascaded nanodisks at telecommunication wavelength1550nm, the filter has a high transmittance (approximately90%) and a high Q factor (approximately60). The cascaded nanodisks support a united resonant (UR) mode. Light is trapped in the middle nanodisk when the UR mode exists. This phenomenon leads to the efficient transmittance and high Q factor of the plasmonic filter. The resonant wavelength and Q factor can be easily modulated by the radii of the nanodisks and the width of the waveguide.In the fifth chapter, the thesis is summarized and outlook of the further studies on nanophotonics devices are discussed.更多还原