用于倾斜入射的波分复用薄膜滤光片的特性及改进

对倾斜入射时窄带薄膜滤光片的特性作了描述 ,由于低折射率间隔层的滤光片 ,倾斜入射时 p偏振分量的通带比s分量更移向短波 ,而高折射率间隔层的滤光片则反之 ,因此可把间隔层同时设计成高、低折射率两种材料 ,或选用适当的中间折射率材料 ,使p分量和s分量两个通带的中心波长重合。设计了用于 2 0°入射角的密集波分复用 (DWDM )滤光片 ,并给出了实验结果。

Characteristics and Improvement of Dense Wavelength Division Multiplexing (DWDM) Thin Film Filters Used in Tilted Incidence

The characteristic of thin film narrowband filters used in tilted incidence is described. The wavelength shift to shorter wavelength in a low index spacer filter for p polarization component is larger than that for s polarization component when filter is tilted. On the contrary, the shift in a high index spacer filter for p component is less than that for s component. Therefore the passbands of a tilted filter can be centered at the same wavelength for two polarization modes by means of using high and low index materials for a spacer, or selecting a moderate index material instead of a spacer. Designs of DWDM filters used for incident angle of 20°are presented, and the experimental results are discussed.