为实现45°入射情况下K9基底上双波段截止分色的特性(截止带波长0.5~0.68 μm、0.73~0.79 μm, 通带波长0.83~0.87 μm), 采用F-P型的带通滤光片膜系结构为初始结构, 与常规设计理念相比有效减少了膜层的数量, 薄膜的高折材料采用TiO2, 低折材料采用SiO2, 以实现双波段截止的目的。膜层的设计层数为23层, 总厚度为2.278 μm, 借助电子束蒸发物理气相沉积法实现了镀制, 利用分光光度计对镀制样品的透过率进行评估。测试结果显示, 截止区(0.5~0.68 μm和0.73~0.79 μm)平均截止深度分别达到了12.57%和20.39%, 通带0.83~0.87 μm波段内的平均透过率达到了91.35%, 样品测试曲线与设计相比, “蓝移”将近10 nm。薄膜样品基本实现了设计目标, 具有双波段截止、高通带透过率的特性。在环境测试中: 薄膜表现出显著的稳定性, 膜层间匹配度适宜。该双波段截止分色滤光片能够应用在一些极端的情况下。

To realize the characters of a dual-band filter that selectively transmit light of wavelengths of 0.83-0.87 μm but cut off the wavelengths of 0.5-0.68 μm and 0.73-0.79 μm on a 45° incident angle on K9 substrate, a type of F-P bandpass filter was chosen to be the initial structure which effectively reduce the number of the thin film compared with the routine design concept. The high index material of titanium oxide (TiO2) and the low index material of silicon oxide (SiO2) were used during the course. The thickness of 23 layers was 2.278 μm. The electron beam physical vapor deposition (EBPVD) was used to fabricate the coatings. The transmittance of the sample was measured by using the spectrophotometer. The average cutoff depth is 12.57% and 20.39% corresponded to the band from 0.5 μm to 0.68 μm and the band from 0.73 μm to 0.79 μm respectively from the test result. The average transmittance is up to 91.35% for the pass band from 0.83 μm to 0.87 μm. It appears almost the same with the designing result that the figure of transmittance shifts to the short wavelength by 10 nm. Beyond this, the edge filter cuts off in dual-band and gets the high transmittance in pass band. In the environmental tests, the coatings match well with each other which is remarkably stable. So, the dual-band cut-off edge filter can be applied in extreme cases.