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纳米金属颗粒及其与金属膜的耦合结构具有比单元结构更优越的物理性质。为了给实验研究纳米银立方体和银膜耦合结构在传感中的应用提供理论依据,运用FDTD方法数值分析了纳米银立方体与银膜耦合体系在波长为514.5 nm的激光激发下的电场性质。结果表明,耦合结构的电场分布与纳米银立方体的大小、及其与银膜间的介质层厚度有关;纳米银立方体与银膜耦合结构局域电场比纳米银立方体的局域电场强;当其间没有介质层时,局域电场主要分布在纳米银立方体的上表面顶点;当有介质层时,局域电场会有部分转向高折射率介质层中。因此,可根据需要,通过调控纳米银立方体的大小及其与银膜间的介质厚度来获得理想的局域电场。
The nano-metal particles and their coupling structure with the metal film have more superior physical properties than the cell structure. In order to provide a theoretical basis for the experimental study on the application of silver-silver and silver-film coupling structures in sensing, the electric field properties of the coupled system of silver nanoparticles and silver films excited by a laser at 514.5 nm were numerically analyzed by FDTD method. The results show that the electric field distribution of the coupling structure is related to the size of the nano-silver cube and the thickness of the dielectric layer between the silver films. The local electric field of the silver nano-cube coupling structure is stronger than that of the silver nano-cube. When there is no dielectric layer, the local electric field mainly distributes on the apex of the upper surface of the nano-silver cube; when there is a dielectric layer, the local electric field will be partially turned into the high refractive index medium layer. Therefore, the desired local electric field can be obtained by adjusting the size of the nano-silver cube and the thickness of the medium with the silver film as needed.