光学仪器  2019, Vol. 41 Issue (5): 47-52 PDF

Near-field focused nano-scattering structure
LIU Chen, WANG Haifeng
School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
Abstract: In order to overcome the limitations of the Mie scattering method based on approximate theoretical analysis in the study of particle size smaller than the incident light wavelength, this paper used the finite difference time domain (FDTD) method based on numerical simulation to scatter nano-scale. The effect of bulk particles on the near-field focused beam was simulated. The FDTD simulation software was used to simulate the light intensity distribution information around the nano-air particles with the focused linearly polarized light as the light source and the spherical nano-air particles embedded in the beam focus point of the bottom surface of the solid immersion lens. A good focus imaging effect is achieved by changing the corresponding simulation conditions.
Key words: linearly polarized light    solid immersion lens    Mie scattering    focusing    FDTD

1908年，德国科学家Gustav Mie基于经典波动光学理论的麦克斯韦方程组和适当的边界条件，推导出了任意成分、任意粒径的均匀介质球形微粒在单色平面波照射下远场散射的严格数学解。经过100多年的发展，米氏散射理论[11]得到了极大的发展，被广泛地应用到微粒检测技术、相位调制技术、辐射制冷技术等各个领域。

1 理论分析

 ${I_s} = \frac{{{{\rm{\lambda }}^2}{I_0}}}{{4{\rm{\pi ^2}}{r^2}}}\left[ {{i_1}\left( \theta \right){\rm{si{n^2}}}\varphi + {i_2}\left( \theta \right){\rm{co{s^2}}}\varphi } \right]$ (1)

 图 1 球形微粒散射 Figure 1 Spherical particle scattering
2 仿真结构设计

 图 2 仿真系统设计图 Figure 2 Design of the simulation system
3 仿真模拟结果与数据分析 3.1 嵌入纳米空气粒子前后对系统聚焦的影响

 图 3 未嵌入和嵌入纳米空气粒子时系统能量强度对比图 Figure 3 Comparison of system energy intensity with and without embedding air nano particles

 图 4 未嵌入和嵌入纳米空气粒子时p矢量能量强度对比图 Figure 4 Comparison of p-vector energy intensity with and without embedding air nano particles

3.2 改变纳米空气粒子的嵌入位置

 图 5 纳米空气粒子相对位置变化时系统能量强度对比图 Figure 5 Comparison of system energy intensity when the relative position of nano air particles changes

 图 6 光强随z值变化的2D曲线图 Figure 6 2D graph of light intensity as a function of z value

3.3 改变纳米空气粒子的尺寸

 图 7 不同纳米空气粒子粒径对系统电场能量强度的影响 Figure 7 Influence of particle size of different air nano particles on electric field energy intensity of system

3.4 改变透镜材料的折射率

 图 8 不同透镜折射率对系统聚焦的影响 Figure 8 Influence of different lens refractive indices on system focusing

3.5 将光源改为聚焦后的径向偏振光

 图 9 未嵌入纳米空气粒子和嵌入时系统能量强度对比图 Figure 9 Comparison of electric field energy intensity with and without embedding air nano particles

4 结　论

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