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微纳光纤具有大比例倏逝场传输的光学特性,相比于普通光纤,其耦合现象更加明显。利用基于有限元法的COMSOL Multiphysics软件对三根平行微纳光纤进行了详细的数值模拟研究。计算结果表明,纤芯间距改变时,三根平行微纳光纤随传输距离变化的功率耦合分布的规律是相似的,都呈周期性分布。纤芯间距不同时,耦合周期发生变化,且随着纤芯间距的增大,耦合周期也逐渐增大。且入射光的偏振态对耦合周期和耦合效率也有一定的影响。利用三根平行微纳光纤的耦合特性,设计了一种3×1微纳光纤耦合器,当选取恰当的纤芯间距和耦合区长度时,3×1微纳光纤耦合器的耦合效率最高可达93.3%。
Micro-nano fiber has a large proportion of evanescent field transmission of optical properties, compared to ordinary fiber, the coupling phenomenon is more obvious. A detailed numerical simulation of three parallel micro / nanofiber optical fibers is carried out using COMSOL Multiphysics software based on the finite element method. The calculation results show that the regularity of the power coupling distribution of the three parallel micro / nano fibers with the transmission distance changes when the core pitch is changed, all of them are periodic distribution. When the core-to-core spacing is different, the coupling period changes, and as the core pitch increases, the coupling period also gradually increases. And the polarization state of the incident light has a certain influence on the coupling period and the coupling efficiency. Using the coupling characteristics of three parallel micro-nano fibers, a 3 × 1 micro-nano fiber coupler is designed. When the proper inter-core spacing and coupling region length are chosen, the coupling efficiency of the 3 × 1 micro-nano fiber couplers can reach the highest 93.3%.