两种亚波长金属波片的透射特性对比

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。

Comparison of Transmission Properties of Two Kinds of Subwavelength Metallic Wave Plates

Based on the equivalent medium theory and surface-plasmon-polariton (SPP) Bloch model, two kinds of novel metallic waveplates are analyzed: two-dimensional rectangular metallic grating and elliptical cylinder metallic grating. First, utilizing the finite-difference-time-domain (FDTD) method, we analyze the relation between characteristics of both waveplates in terms of the transmittance and phase retardation and parameters of the incident light in terms of the wavelength and polarization angle, especially transmission properties of both gratings functioning as quarter-wave plates. Simulation results show that both structures can act as quarter-wave plates when the input polarization angle is 75°. The corresponding transmittances of rectangular and elliptical cylinder gratings are 0.77 and 0.67, respectively. In addition, both gratings exhibit relatively flat transmission spectra within the wavelength range from 550 nm to 800 nm in the presence of different input polarization angles.