亚波长结构是特征尺寸小于工作波长的连续阵列浮雕结构, 可看成是一层折射率均匀的介质层, 仅存在零级的透射和反射衍射。基于等效介质理论和严格耦合波理论介绍了亚波长抗反射结构。为提高111μm波长太赫兹辐射(2.7THz)的透过率, 在硅表面设计了亚波长抗反射结构。该结构的透射率和反射率由其浮雕结构的周期、高度和占空比确定。利用等效介质理论和严格耦合波理论对其结构参数进行了优化设计。当周期为27μm、高度为13μm、占空比为0.75时, 得到了99.05%的太赫兹辐射透过率。

Sub wavelength structure (SWS) is defined as periodic structure that contains a pattern with smaller period size compared to light wavelength. The structure appears as a dielectric layer with homogeneous refractive index and the zeroorder diffraction. In this paper, SWS was introduced based on effective medium theory and rigorous coupled-wave theory. In order to increase the transmission of terahertz (THz) radiation at wavelength of 111μm (2.7THz), SWS on Si surface was designed. The transmittance and reflectance of the structure depended on its period, height and filling factor. The parameters of the SWS were optimized by effective medium theory and rigorous coupledwave theory. The results show that a transmittance of 99.05% was achieved by the SWS with a period of 27μm, a height of 13μm and a filling factor of 0.75.