图  1  基底的结构示意图　(a)与其对应的参数示意图(b)

Figure  1.  Sketch of the structure(a) with the defined parameters and coordinate axis(b).

图  2  圆盘的参数不变(r₁ = 63 nm, r₂ = 97 nm, d = 10 nm, h₁ = 50 nm)改变导电结参数时散射系数的变化　(a) $ \theta $ = 45⁰, h₂ = 50 nm, O_{(x, y)} = (100, 100), 改变结的宽度l从30到50 nm; (b) l = 40 nm, h₂ = 50 nm, O_{(x, y)} = (100, 100), 改变倾斜角度 $ \theta $ 从25⁰到45⁰; (c) l = 40 nm, $ \theta $ = 45⁰, h₂ = 50 nm, 改变中心坐标O_{(x, y)}从(70, 70)到(110, 110); (d) l = 40 nm, $ \theta $ = 45⁰, O_{(x, y)} = (100, 100), 改变结厚度h₂从30到50 nm

Figure  2.  When the parameters of the disc are unchanged (r₁ = 63 nm, r₂ = 97 nm, d = 10 nm, h₁ = 50 nm) that the scattering spectrum depond on geometrical parameters: (a) Vary l with $ \theta $ = 45⁰, h₂ = 50 nm, O_{(x, y)} = (100, 100); (b) vary $ \theta $ with l = 40 nm, h₂ = 50 nm, O_{(x, y)} = (100, 100); (c) vary O_{(x, y)} with l = 40 nm, $ \theta $ = 45⁰, h₂ = 50 nm; (d) vary $ {h}_{2} $ with l = 40 nm, $ \theta $ = 45⁰, O_{(x, y)} = (100, 100).

图  3  入射光不同偏振角度时的相同参数(l = 35 nm, h₂ = 50 nm, O_{(x, y)} = (100, 100), r₁ = 63 nm, r₂ = 97 nm, d = 10 nm)结构的散射系数, 偏振角度定义为入射光偏振方向与结构Y轴夹角

Figure  3.  . Scattering spectra for various excitation polarizations with the same parameters (l = 35 nm, h₂ = 50 nm, O_{(x, y)} = (100, 100), r₁ = 63 nm, r₂ = 97 nm, d = 10 nm), and the polarization angle is defined as the angle between the polarization direction and the Y-axis.

图  4  (a) 入射光偏振方向沿基底的Y轴方向时与入射光偏振方向与基底的Y轴的夹角为45⁰时基底表面912 nm, 1064 nm, 1275 nm三个波长处与1064 nm时基底中心YZ横截面处的电场强度空间分布; (b) 当入射光偏振方向沿基底的Y轴方向夹角θ为0°, 15°, 30°, 45°时基底表面对应的增强G_SECARS因子的对数空间分布图

Figure  4.  (a)The spatial distributions of enhanced electric-filed amplitude (|E/E₀|) in the top surface plane of the structure at three characteristic wavelengths for two polarizations; (b) the corresponding SECARS map for various polarizations. From the top to bottom, the polarization angle θ equals to 0°, 15°, 30°, 45°, respectively.