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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。
The subwavelength structure is a continuous array of relief structures with feature sizes smaller than the working wavelength. It can be seen as a uniform dielectric layer with only zero order transmission and reflection diffraction. Based on equivalent medium theory and strict coupled wave theory, the subwavelength antireflection structure is introduced. In order to improve the transmittance of terahertz radiation (2.7THz) at 111μm wavelength, a subwavelength anti-reflection structure was designed on the silicon surface. The transmittance and reflectivity of the structure are determined by the period, height and duty cycle of its relief structure. The structural parameters were optimized by using equivalent medium theory and strict coupled wave theory. When the period is 27 μm, the height is 13 μm and the duty cycle is 0.75, a terahertz radiation transmittance of 99.05% is obtained.