TE激励下金属光栅电荷振荡的异常透射及其表面波分析

Surface wave and extraordinary transmission through metallic gratings with oscillating charge under TE polarization excitation

利用时域有限差分法,对TE偏振光(电场平行狭缝方向)激励下,不同结构和参数的带电介质亚波长一维金属光栅的光场分布进行了数值模拟实验。根据金属表面电荷分布理论和表面波理论对此现象进行了物理机理分析,通过分析可以得出在金属狭缝处产生柱面表面波,这种表面波可以突破衍射极限,从而引起异常透射;并且根据Ag的表面电荷分布及其激发机理分析,得到了透射峰位置与介质覆层厚度变化的动态响应以及金属薄膜厚度改变时透射率与波长变化的动态关系,确定了柱面表面波是该异常透射现象产生的一个重要原因。理论分析与模拟实验结果一致,从而为TE偏振光激励下的异常透射机理深入研究和结构参数的选择提供了较好的理论依据。

Numerical simulation experiments on optical field distribution of one-dimensional metallic gratings with dielectric substances and sub-wavelength slits which are different in structure and parameter under transverse electric（TE） polarization excitation were carried out by using the method of finite-difference time domain.Physical mechanism was analyzed based on the theory of charge distribution on metal surface and the surface wave theory.The analysis showed that cylindrical surface waves were generated in metal slits and such kind of surface waves could break the diffraction limit to cause extraordinary transmission.The dynamic response of the dielectric cladding thickness to the transmission peak position and the dynamic relationship between the transmissivity and the wavelength when varying the thickness of metallic thin film were found by analyzing the surface charge distribution and excitation mechanism of Ag,thus the cylindrical surface wave was confirmed as one of the important factors that may cause extraordinary transmission.The theoretical analysis is consistent with the si-mulation results,which provides a good theoretical basis for an further study on the mechanism of extraordinary transmission and the selection of structural parameters under TE polarization excitation.