【作者】 胡昌奎；

【导师】 刘德明；

【作者基本信息】 华中科技大学 ， 光学工程， 2010， 博士

【摘要】 随着纳米技术的发展和表面等离子体光子学的兴起,光与金属微纳米结构相互作用时呈现出的新颖光学效应及其应用已成为一个研究热点,而周期为波长量级的金属光栅则是人们在研究光与周期性金属结构相互作用时常采用的一种结构模型。本论文采用严格耦合波分析法(Rigorous Coupled Wave Analysis, RC WA),对基于纳米金属光栅结构的表面等离子体共振(Surface Plasmon Resonance, SPR)效应及其传感应用进行了深入的研究。本论文的主要研究内容包括以下几个方面：(1)运用数值模拟的方法研究了光栅耦合激发表面等离子体波的结构模型中光栅周期、光栅深度、入射介质折射率以及不同的金属材料对表面等离子体共振特性的影响,并通过理论分析给出了相应的物理解释；在分别研究了基于金和铝两种金属材料的光栅耦合表面等离子体传感器传感特性的基础上,提出了一种Al-Au双金属层结构的光栅耦合表面等离子体共振传感模型。数值分析表明,该传感器具有良好的传感特性,其角度灵敏度可达到187.2°／折射率单位,共振吸收峰的半峰值全宽(Full Width at Half Maximum, FWHM)仅为0.93°,且共振角与待测分析物的折射率具有良好的线性关系,线性相关系数达到0.99828。(2)在传统Kretschmann结构模型的基础上,通过金属膜层表面的光栅将表面等离子体波共振耦合为辐射模,并研究了光栅高度、光栅周期及其金属膜层厚度对耦合效率的影响；通过对介质光栅共振耦合表面等离子体波为辐射模的结构参数进行优化,得到了74.57%的峰值耦合效率。当自然光以共振角度入射时,此结构具有良好的偏振分束功能,其反射消光比和透射消光比分别可达到30dB和42.2dB；此外,利用表面等离子体共振条件对金属膜层周围介质折射率的变化高度敏感的特点,构建了一种透射型表面等离子体共振传感模型,并对金属光栅和介质光栅两种不同结构的透射型表面等离子体共振传感器的传感特性进行了对比分析,提出采用低折射率棱镜的方法来提高这种传感器的角度灵敏度。(3)基于连续膜金属光栅结构,提出了一种棱镜耦合和光栅耦合相结合的表面等离子体激发模型,分析了这种结构在小光栅周期和大光栅周期两种情况下的表面等离子体共振特性,并通过理论分析给出了相应的物理解释；研究了基于连续膜金属光栅结构的表面等离子体共振传感器的灵敏度增强特性,并在大周期光栅情况下引入双共振吸收峰测量法,大幅提高了表面等离子体共振传感器的灵敏度。数值模拟显示,其角度灵敏度可达到153.23°／折射率单位,且共振角与待测分析物的折射率具有较好的线性关系,线性相关系数达到0.99997。(4)针对表面等离子体共振传感系统对入射光波偏振态的要求,基于亚波长金属光栅的形式双折射效应设计了一种用于可见光波段范围的亚波长铝光栅偏振器。数值计算结果表明该器件在整个可见光波段范围内TM偏振光的透射率大于75%,透射消光比大于38dB,且器件还具有较大的可接收入射角范围；系统地分析了光栅制作误差对该器件偏振特性的影响,并采用铝栅条氧化模型分析了铝栅条氧化前后器件偏振特性的变化。结果显示该器件具有一定制作误差容忍度,且铝栅条氧化后器件仍然具有良好的偏振特性。更多还原

【Abstract】 With the development of nanotechnology and the rise of plasmonics, the study of the interaction between light and metal micro/nano structure has become a hot subject in recent years. The metallic gratings with the period on the same order of wavelength are a basic structure that is employed in the research of the interaction between light and periodic metallic structure. In this paper, by using rigorous coupled wave analysis (RCWA), the surface plasmon resonance (SPR) sensors and polarizers based on nano metallic surface-relief gratings are analyzed.The main research works are as follows:Firstly, based on numerical simulation and theoretical analysis, the influences of the grating period, grating height, the refractive index of incident medium and different metal materials on the resonant properties are analyzed and explained in the scheme of excitation of surface plasmon polaritons (SPPs) using a metallic grating; a novel grating-coupled SPR sensor with Al-Au bimetallic layer is proposed, and the refractive index sensitivity of the SPR sensor is predicted to be 187.2 degree per refractive index units (°/RIU), the full width at half maximum (FWHM) of the resonant absorption peaks is 0.93°. In addition, the shift of resonance angle as the refractive index of the medium surrounding the metal surface varied is completely linear, and the correlation coefficient is 0.99828 according to linear regression analyses.Secondly, based on the scheme of excitation of SPPs using a prism coupler and the attenuated total refection method, the principle of resonant coupling surface plasmon wave to radiation modes by use of gratings is investigated, the influences of the grating height, grating period and the thickness of metal layer on coupled efficiency are analyzed. A peak coupling efficiency of 74.57% is obtained by use of a dielectric grating with optimized structural parameters, the configuration allows TM-polarized light to be transmitted and TE-polarized light to be reflected, the extinction ratio for radiation modes and reflection modes are 30dB and 42.2dB respectively. The configuration can be used as a transmission-type SPR sensor because the resonance condition is highly sensitive to the variations of the medium surrounding the metal surface, and the properties of the sensor with the dielectric gratings and metallic gratings are investigated respectively. In addition, a method to enhance the sensitivity of the transmission-type SPR sensor by use of low refractive index prism is proposed.Thirdly, we propose a SPPs excitation scheme based on continuous film metallic gratings, in which the prism coupling method and grating coupling method are combined. The properties of surface plasmon resonance are analyzed in condition of small period grating and large period grating respectively, and the physical interpretation related to the results is provided according to theoretical analysis. The sensitivity enhancement of SPR sensor with continuous film metallic gratings is investigated. When the period of gratings is comparatively large, the method of double dips is adopted in order to enhance the sensitivity of SPR sensor. It is found that the refractive index sensitivity of the SPR sensor is predicted to be 153.23°/RIU, and the shift of resonance angle as the refractive index of the medium surrounding the metal surface varied is completely linear, and the correlation coefficient is 0.99997 according to linear regression analyses.Finally, based on the effect of form-birefringence of subwavelength metallic gratings, an Aluminum wire-grid polarizer for visible wavelengths is proposed, and the theoretical research shows that aluminum wire-grid polarizer has high transmission coefficient and extinction ratio over the visible spectrum, as well as uniform performance with wide variations in the angle of incidence. In addition, the influences of the fabrication error of gratings and the oxide layers coated on the wire on the polarization properties are analyzed. It is shown that the small fabrication errors do not have a significant effect on the polarization properties of wire-grid polarizer, and the polarizer with oxide layers coating on the wires still provides high performance.更多还原