Cui Mingjie, Mo Zhifeng, Zhao Nan, Xia Changming, Hou Zhiyun, Zhou Guiyao
Opt Express. 2021 Mar 1;29(5):6542-6552. doi: 10.1364/OE.417155.
We propose a helically twisted pig-nose-shaped core microstructured optical fiber (HPC-MOF) for orbital angular momentum (OAM) mode generation. It comprises seven air-hole rings hexagonally arranged with two air holes and one air-hole ring replaced, forming two cores in a line 3 µm from the fiber center and one ring-shaped core. The fiber is helically twisted along the rotation axis. In this fiber, supermodes in inner dual-core can be coupled to high-order modes in outer ring-core, yielding OAM ring-shaped modes at different certain wavelengths, and various OAM modes at different twist rates were investigated in this paper. We demonstrate the distinct coupling differences of symmetric and antisymmetric supermodes in inner dual-core when the supermode coupled to ring-core mode. A modal matching rule is presented to characterize the coupling differences, which is suitable for describing supermode coupling characteristics in HPC-MOFs. Compared to conventional methods, these properties indicate that the fiber can generate higher-order OAM modes and more easily integrate into all-fiber optical communication systems, with potential in OAM generators, light-controlling devices, and integrated optics applications.
我们提出了一种用于产生轨道角动量（OAM）模式的螺旋扭曲猪鼻形芯微结构光纤（HPC-MOF）。它由七个六边形排列的气孔环组成，其中两个气孔和一个气孔环被替换，在距光纤中心3 µm处形成两个排成一行的芯和一个环形芯。该光纤沿旋转轴螺旋扭曲。在这种光纤中，内部双核中的超模式可以耦合到外部环形芯中的高阶模式，在不同的特定波长下产生OAM环形模式，并且本文研究了不同扭曲率下的各种OAM模式。当超模式耦合到环形芯模式时，我们展示了内部双核中对称和反对称超模式的明显耦合差异。提出了一种模态匹配规则来表征耦合差异，该规则适用于描述HPC-MOF中的超模式耦合特性。与传统方法相比，这些特性表明该光纤可以产生高阶OAM模式，并且更容易集成到全光纤光通信系统中，在OAM发生器、光控设备和集成光学应用中具有潜力。
