提出一种基于非对称双芯光子晶体光纤的宽带定向耦合器结构。这种结构是通过将原来对称型的双芯光子晶体光纤结构中的一个空气孔增大的方法实现的。数值结果表明,这种耦合器工作带宽可达370 nm,且偏振相关损耗和均匀性分别小于0.2和0.5 dB。同时,这种结构允许光纤具有较大的制作误差。例如,光纤长度可以偏离设计长度(7.7 mm)的10%。

A novel broadband directional coupler based on an asymmetric dual-core photonic crystal fiber (PCF) is proposed. The asymmetry in the fiber is introduced by the enlargement of one air-hole in dual-core PCF. Numerical investigation demonstrate that broadband directional coupling with spectral width as large as 370 nm and polarization-dependent loss and uniformity lower than 0.2 and 0.5 dB, respectively, can be achieved. In addition, the proposed fiber shows large tolerance to the variation of the fiber parameters. In particular, the fiber length allows at least 10% derivation from the proposed fiber length of 7.7 mm.