根据薄膜窄带滤光片在倾斜入射时的特性,通过改进间隔层膜系结构调整其等效折射率,可以设计出具有稳定透射峰值和带宽的角度调谐窄带滤光片。倾斜入射时窄带滤光片透射光的S和P偏振分量的中心波长会随着入射角度的增大出现分离现象,产生较大的偏振相关损耗。分析了偏振分离现象出现的原因和其与滤光片等效折射率的关系,提出了消除偏振分离现象的方法。根据薄膜矩阵理论建立了分析模型并提出了一种该可调滤光片的设计方法,根据开发的程序优化设计并制备了一组用于100 GHz密集波分复用(DWDM)系统的低偏振相关损耗的四腔角度调谐窄带滤光片,实验结果证明其满足设计要求并有接近20 nm的可调范围。

According to the characteristics of the thin film narrowband filter, the angle-tuned filter with stable transmission peak and bandwidth can be designed by amelioration of the structure of the stack and adjust of effective refractive index of the spacer. At the same time, the central wavelength of S-polarization and P-polarization will separate when the filter is tilted, which causes the polarization dependent loss. The phenomena of polarization separation and its relationship to the effective refractive index of the filter are analyzed. A method about eliminating the polarization separation is presented. Theoretical analysis model is built up and an angle-tuned filter design method is provided based on the theory of thin film matrix. A 100 GHz dense wavelength division multiplexing (DWDM) four-cavity angle-tuned narrowband filter with low polarization dependent loss is optimized and fabricated based on the programme. The experimental results prove it meets the demand of design and its tunable range is about 20 nm.