理论设计了介质光栅/金属薄膜与银纳米立方体复合结构, 通过有限元方法数值模拟计算了该结构中的超高电场增强因子.使用442 nm波长的激光作为表面等离子体的激发光源, 研究不同尺寸银纳米立方体的消光谱以及不同光栅周期和厚度的反射光谱, 得到的该复合结构的最优参数为: 光栅周期312 nm, 厚度90 nm, 银纳米立方体70 nm.在最优参数条件下, 数值模拟了复合结构中的电场增强分布, 介质光栅/金属薄膜与银纳米立方体复合结构由于存在局域表面等离子体和传播表面等离子体的共振耦合, 使得光栅脊与银纳米立方体下顶点接触处热点的电场增强因子高达1.53×106.该复合结构产生的超高电场增强因子, 有望应用于表面增强拉曼散射的研究.

A composite structure of dielectric grating/metal film with silver nanocubes is theoretically designed, and the ultrahigh electric field enhancement factor in the composite structure is numerically simulated using the finite element method. The surface plasmons are excited by the laser with wavelength of 442 nm. By discussing the extinction spectrum of the silver nanocubes with different sizes, and the reflection spectra of the grating with different period and thickness, the optimal parameters are selected, which the side length of silver nanocubes is 70 nm, the period of grating is 312 nm and the thickness is 90 nm. Under the condition of optimal parameters, electric field intensity distribution in the composite structure is calculated. For the resonant coupling of local surface plasmon and propagation surface plasmon in the dielectric grating/metal film with silver nanocubes composite structure. The electric field enhancement factor of hot spot is as high as 1.53×106, which exists in the position between grating ridge and the lower vertexes of silver nanocube. The ultrahigh electric field enhancement generated by the composite structure has the potential to be applied to the study of surface-enhanced Raman scattering.