【作者】 高兴宇；

【导师】 刘书桂；

【作者基本信息】 天津大学 ， 测试计量技术及仪器， 2010， 博士

【摘要】 表面等离子体是纳米光子学重要的研究领域之一,也是纳米探测技术、生物传感技术、超分辨率聚焦与成像技术和纳米波导技术等众多前沿课题的重要基础理论之一。金属纳米结构在入射光作用下激发表面等离子体,其光学性质取决于金属色散介质的相对介电系数、纳米结构的尺寸和形状、金属结构周围介质的折射率以及入射光的偏振态等因素,因而表面等离子的产生、分布和传导特性相比普通光波更加复杂。在高数值孔径物镜聚焦区域电磁场存在三个方向的偏振分量,因而在聚焦区域内的金属纳米结构会受到不同偏振方向电场的作用而激发表面等离子体。本论文针对高数值孔径物镜聚焦区域三维电磁场分布的特点,提出了将计算聚焦区域光场分布的Debye理论与时域有限差分方法(FDTD)相结合的新的研究方法,仿真分析金属纳米结构在聚焦光束作用下激发表面等离子体的机理、特性和新的光学现象,并进行了利用表面等离子体的光学特性进行亚微米尺度精密测量研究的初步探讨。本论文主要工作如下:1、利用总场/散射场方法将用Debye理论计算的线偏振聚焦光束和径向偏振聚焦光束作为入射波源代入三维FDTD计算空间中,验证了用FDTD计算聚焦区域光场分布的有效性和精确性。2、介绍了表面等离子体的经典电磁理论和色散介质的相对介电系数模型,并用多种方法将这些模型实现于FDTD程序中.。用表面等离子体共振(SPR)模型仿真算例比较了各种方法的优缺点,其中PLRC方法在计算精度和速度上都是最优的。3、提出了用双平行纳米棒结构产生的局域表面等离子体(LSPs)调制焦点区域光场分布的新方法,在等离子体波导外侧得到了超分辨率的焦点。利用不同宽度的双纳米棒产生的LSPs的焦点分布不同,通过探测焦点可以反之推测双纳米棒的宽度,其测量分辨率达4.67nm。4、利用双纳米棒结构超长波导将焦点区域光场能量传导到1μm之外的远场区域,并且还可以传导到垂直于光轴方向的轴外区域,大大拓展了焦点区域光场分布范围。更多还原

【Abstract】 The surface plasmons(SP) is one of the important research areas in nano-photonics. It is also one of the foundamental theories for the nano-detection, biosensor, super-resolution focusing and imaging, and nano-waveguide technologies. The metallic nano-structures excite the SP under the interaction with the incident light wave. The optical properties of SP are decided by the relative permittivity of metallic dispersive media, the size and shape of the nano-structure, the refractive index of the media surround the metallic nano-strucure, and the polarization of the incident light, so that its excitation, distribution and propagation properties are complicated compare to normal light wave. There are three polarization components in the focal region of high numerical aperture objective. The metallic nano-structures in the focal region would interact with different polarized electric fields and excite the SP.In this thesis, according to the properties of 3D distributions of the electromagnetic field in the focal region of high numerical aperture objective, we demonstrate the new aproach that combine the Debye theory for calculating the optical field distribution of focal region with the finite difference time domain(FDTD) method. This new method can be used to investigate the excitation machnism and new optical phenomenons of SP excited by the metallic nano-structures under the illumination of focal beams. Further more, the application of the optical properties of SP for the precision measurement in the submirometer scale will be investigated primarily.The main work of this project is listed as:1、The electrical field distributions of linearly polarized and radially polarized focal beams calculated by vectorial Debye theory are induced into 3D FDTD simulation space using the total field/scattering field method. The effect and precision of the FDTD simulation for the optical distribution of the focal region are testified.2、The classical electromagnetic theory of surface plasmons and the relative permittivity models of dispersive media are introduced. These relative permittivity models are implemented into FDTD program by several methods such as PLRC, ADE and SO. The simulation example of surface plasmons resonance model is applied to compare the simulation precision and speed of these methods are analyzed. The result shows the PLRC method is the best among them.3、The modulation of the focal region by the localized surface plasmons(LSPs) excited by the two parallel nanorods structure is demonstrated. A super-resolved focus can be obtained outside the nano-plasmonic waveguide. The optical fields of different distances between the two nanorods show different distributions. The precise detection of different LSPs patterns can be used to measure the different distances between the nanorods, which shows that the measurement resolution is less than 5nm.4、The optical field energy of the focal region can be transferred to the far field futher than 1μm by the super-long two nanorods waveguide structure. The“L”-shaped two nanorods waveguide transfer the electromagnetic field from the focal region to the direction perpendicular to the optical axis, which widely broaden the distribution region of the focal spot.更多还原