近红外消偏振分光膜设计近红外消偏振分光膜设计

大角度倾斜入射时，光学薄膜表现出强烈的偏振效应。入射光S分量和P分量的反射率和透射率曲线，以及反射或透射引起的两个分量的相位变化都不再相同，彼此有一定的偏振分离。通过对产生偏振效应内在原因的分析，采用一个在近红外波段对于45倾斜入射光的S分量和P分量等效导纳非常接近的膜系结构，结合单纯形法优化算法，设计得到一个1 500～1 600 nm范围内反射率都是50％的近红外消偏振分光膜。结果显示，在45入射时，S分量和P分量的反射率曲线偏振分离小，反射和透射引起的相位变化也控制在很小范围。

Design of near-infrared non-polarizing beam splitter

Under large-angle oblique incidence, the optical thin films exhibit strong polarization effects. The reflectance and transmittance for both S- and P-components will exhibit some polarization deviations. The reflection-and transmission-induced phase retardances will exhibit the same behavior. After the analysis of the physical essence within the polarization effects, a near-infrared nonpolarizing beam splitter with a reflectance of 50% in 1 500-1 600 nm spectral range was designed. It adopted a thin film stack with approximately equal equivalent admittances for both S- and P-components with the aid of simplex optimization algorithm. According to the results, in the working range of spectrum with the incident angle of 45°, the splitter maintains a very low polarization ratio, and both the reflectance( transmittance) curve deviation and the reflection (transmission)-induced phase change are small.