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综合等效介质理论和表面等离子激元(SPP)Bloch模型,对比分析了两种新的亚波长光栅结构:二维矩形金属光栅和二维椭圆柱金属光栅。利用时域有限差分(FDTD)算法,对比分析了两种结构的透射率及其相位延迟与入射光波长及偏振角变化的关系,尤其两种结构实现λ/4波片功能所对应的透射特性。仿真结果表明,当入射光偏振角为75°时,两种结构均可实现λ/4波片功能,此时二维矩形和椭圆柱金属光栅的透射率分别为0.77和0.67,表明二维矩形金属光栅比椭圆柱光栅具有更好的透射效果。对应550～800nm的入射波长,两种光栅在各自允许的入射偏振角范围内均表现了较为平坦的宽带透射特性。
Based on the Bloch model of surface plasmon polariton (SPP) and equivalent medium theory, two new subwavelength grating structures are compared and analyzed: two-dimensional rectangular metal grating and two-dimensional elliptic cylindrical metal grating. The time-domain finite difference (FDTD) algorithm is used to analyze the relationship between the transmittance and the phase delay of the two structures and the variation of incident light wavelength and polarization angle. In particular, the transmission characteristics corresponding to the λ / 4 wave plate function of the two structures . The simulation results show that the λ / 4 wave plate function can be realized by both structures when the polarization angle of incident light is 75 °. At this time, the transmissivities of two-dimensional rectangular and elliptical metallic gratings are 0.77 and 0.67 respectively, indicating that the two-dimensional rectangle Metal grating has better transmission effect than elliptic grating. Corresponding to the incident wavelength of 550 ~ 800nm, the two gratings exhibit relatively flat broadband transmission characteristics within their respective allowed angles of incidence.