Fig. 1. SPPs field excited by rectangular nanoslit: (a) Electric field intensity along the L curves in the x and y direction with the x-direction linearly polarized light incident; (b) electric field excited by the incident light in the x direction; (c) electric field excited by the incident light in the y direction. 矩形纳米狭缝激发的SPPs场　(a) x方向线偏振光入射下x和y方向电场强度随L的变化; (b) x方向线偏振光入射激发的场; (c) y方向线偏振光入射激发的场

Fig. 2. Schematic diagram of excitation of SPPs by (a) circular slit, (b) spiral slit, (c) rotating rectangular nanoslit arrays under the incidence of left-handed circularly polarized light; (d) schematic diagram of double-ring rectangular nanoslit arrays.左旋圆偏振光入射下, (a) 圆狭缝、(b) 螺旋线狭缝、(c) 旋转排列的矩形纳米狭缝阵列激发SPPs原理示意图; (d) 矩形纳米狭缝双圆环阵列结构示意图

Fig. 3. Schematic diagram of compound focusing structure: (a) Two-dimensional top view; (b) sectional view.复合聚焦结构示意图　(a) 二维俯视图; (b) 截面侧视图

Fig. 4. Variation of the center electric field with the difference of slit depth.中心电场随狭缝深度差值变化趋势

Fig. 5. Simulation diagram of left-hand circularly polarized light incident structure: (a) Electric field distribution diagram; (b) cross-section curve of electric field intensity.左旋圆偏振光入射结构仿真图　(a) 电场分布图; (b) 电场强度切面曲线图

Fig. 6. Electric field distribution excited by linearly polarized light in different polarization directions: (a) ; (b) ; (c) ; (d) . 不同偏振方向线偏振光激发的电场分布　(a) ; (b) ; (c) ; (d)

Fig. 7. Simulation curves of linearly polarized light incident structure: (a) Section curves of electric field intensity; (b) curve of the intensity of the central focal point changing with . 线偏振光入射结构仿真曲线　(a) 电场强度切面曲线; (b) 中心聚焦点强度随 变化曲线

Fig. 8. Comparison of the excitation field intensity curves of the simple structure and the composite focusing structure.简单结构和复合聚焦结构激发场强度曲线对比