针对薄膜滤光片倾斜入射时产生的偏振光中心波长分离现象和偏振相关损耗, 本文利用等效层理论设计了倾斜入射下中心波长消偏振的100 GHz信道间隔滤光片膜系结构, 实现了薄膜滤光片的角度和波长调谐。首先通过相位关系分析, 计算了滤光片间隔层的消偏振等效折射率, 实现了不同偏振光中心波长的对准。然后, 根据等效层理论, 设计三层对称膜层结构实现了对间隔层中心波长消偏振等效折射率的替换。与原有的五层规整低偏振薄膜滤光片相比, 本文提出的膜系结构更为简单, 对消偏振等效折射率的替换更为精确。仿真和实验结果表明: 该膜系结构的薄膜滤光片能实现0~20°倾斜入射的偏振光中心波长对准, 偏振光波长偏离度小于0.03 nm, 波长调谐范围能达到35 nm。

When a thin-film filter is used in oblique incidence, the central wavelengths of the polarization light will be separated obviously, and it will cause serious polarization dependent loss. Therefore, this paper designs a 100 GHz channel spacing stack to depolarize in the central wavelength based on the equivalent layer theory and to realize the angle and wavelength tunes of the thin film filter. Firstly, the depolarization equivalent refractive index in the space layer of the filter was calculated by a phase analysis and to complement the alignment of the different polarization lights. Based on the equivalent layer theory, a symmetric three layer stack was designed to replace the depolarization equivalent refractive index of the spacer. As comparing with the original five layer low polarization thin film filter, the three layer spacer stack is simpler, and it is more accurate to replace the depolarization equivalent refractive index. The simulation and experimental results indicate that the stack can align the polarization light central wavelength from 0° to 20°, in which the polarization light separation is less than 0.03 nm and the wavelength tuning range reaches 35 nm.