提出了一种同时基于全内反射和光子带隙效应两种导光机制的双芯光子晶体光纤(PCF),并采用全矢量有限元法对其耦合特性进行了分析。该种光子晶体光纤双芯间的耦合不同于基于单一导光机制的双芯光子晶体光纤,出现了超模交替截止、耦合长度存在极大值等现象,光纤两纤芯间高折射率柱的谐振在双芯间的耦合过程中起着重要的作用。通过改变光纤中空气孔的大小及间距可以显著改变光纤的耦合长度,而改变高折射率柱的折射率可对耦合长度极大值的位置进行调节。

A dual-core photonic crystal fiber based on total internal refraction and photonic bandgap effect simultaneously is proposed,and its coupling properties are investigated by use of a full-vector finite element method. It is found that the coupling between the two cores of this photonic crystal fiber is different from that of other fibers based on single light-guiding mechanism. This fiber presents novel phenomena such as alternative cutoff of odd and even supermodes,existence of coupling length maxima and so on. The resonance of high-index inclusion between the two cores plays an important role in the coupling. The coupling length of the fiber can be changed significantly by tuning the sizes of air holes and distance between two air holes,and the locations of coupling length maxima can be shifted by adjusting the refractive index of high-index inclusion.