基于角度调谐的光子晶体滤波特性研究

Research on Filter Characteristics of Photonic Crystal with Angle Tuning

提出一种含CaF2缺陷层的一维光子晶体结构,可用于光通信波段的可调谐滤波。通过传输矩阵理论对滤波器透射特性进行分析,结果表明:随着周期数目的增加,光子晶体禁带截止度增强,缺陷模半高宽逐渐变窄,同时缺陷层厚度增加使缺陷峰的位置均匀红移;正入射时,所设计滤波器结构的光子禁带范围是1 170~2 150nm;当入射角增大至掠入射过程中,TE模式全角度光子禁带为1 170~2 035nm,TM模式全角度光子禁带为1 170~1 640nm,表明TM模式禁带对入射角度的变化较敏感。研究发现,选取较大的入射角度或增加光子晶体周期数可以使TM,TE模式透射峰完全分离,通过角度调谐方式可实现光通信S波段两种模式的滤波。该光子晶体滤波器具有高透射率,窄半高宽,宽调谐范围的滤波特性,可有效提高传统滤波器的滤波性能。

A one-dimensional photonic crystal filter with calcium fluoride defect layer is proposed for optical communication.The transmission characteristics of the filter are analyzed on the basis of transfer matrix theory and the results suggest:with the increase of the period number of photonic crystal,the rejection rate of the band gap is increased and the FWHM of defect mode is gradually narrowing;the position of the defect peak gets red shifted uniformly with the augment of defect layer thickness.At normal incidence,the photonic band gap of the designed filter structure ranges from 1 170 nm to 2 150nm;as the incident angle increases to grazing incidence,the omnidirectional photonic band gap ranges from 1 170 nm to 2 035 nm for TE mode and 1 170 nm to 1 640 nm for TM mode,which shows that the forbidden band of TM mode is more sensitive to the change of incident angle.It is also found that the transmission peak of TM and TE mode will become separate with a higher incident angle or larger period number of photonic crystal.The tunable filter can be realized in S band of optical communication through angle tuning.The photonic crystal filter has high transmittance,narrow FWHM,wide tuning range,and can effectively improve the traditional filter performance.