二维抗反射亚波长周期结构光栅的设计分析

Design consideration of two-dimensional anti-reflective subwavelength periodic gratings

利用严格耦合波理论(RCWA)和等效介质理论(EMT)研究了二维抗反射亚波长周期结构光栅的设计问题。以立方体和柱状单台阶网格光栅和金字塔形及圆锥形多台阶光栅为例,主要研究了占空比和表面面形对反射率的影响。通过计算发现,当光栅周期足够小的时候,光栅面形对反射率没有影响,同时占空比严重影响着光栅的特性,这对设计制造抗反射光栅非常有用。同时也研究了等效介质理论的适用性。

This paper investigates the design of a two_dimensional anti_reflective subwavelength grating, by means of RCWA and EMT, take for example, the square_pillar and columned binary gratings, and pyramidal and coned multi_level gratings, the impact of filling factor and surface profile on the reflectance of a grating are mainly considered. It is shown that surface profile has no effect on the reflectivity when the period is sufficiently small, but the wavelength and the filling factor have an important impact on the diffraction characteristics of the grating. So it is very important to design an anti_reflective grating. The validity of EMT is also investigated in the paper.