Heng Xiaobo, Gan Jiulin, Zhang Zhishen, Li Jiong, Li Muqiao, Zhao Hua, Qian Qi, Xu Shanhui, Yang Zhongmin
Opt Express. 2018 Jun 25;26(13):17429-17436. doi: 10.1364/OE.26.017429.
An all-fiber scheme for stable orbital angular momentum (OAM) beam generation and propagation is proposed and demonstrated. This scheme is based on a self-designed and manufactured graded-index few mode fiber (GI-FMF) and compatible mode selection coupler (MSC). The MSC, which consists of a conventional single mode fiber (SMF) and the GI-FMF, can effectively couple the fundamental mode in the SMF to the desired OAM mode in the GI-FMF based on phase matching condition. Meanwhile, the GI-FMF breaks the degeneracy between the desired eigenmodes and neighboring vector modes, thereby allowing the preservation and propagation of the selectively excited OAM modes. As a proof-of-principle, we have implemented an all-fiber device operating in stable OAM modes with |l| = 1. The experimental results show stable propagation of OAM beams with the mode purity of ∼95% and bandwidth of 100 nm. This all fiber device could be useful for further development of wide bandwidth OAM mode division multiplexed application.
提出并演示了一种用于稳定产生和传输轨道角动量（OAM）光束的全光纤方案。该方案基于自行设计制造的渐变折射率少模光纤（GI-FMF）和兼容模式选择耦合器（MSC）。由传统单模光纤（SMF）和GI-FMF组成的MSC，能够基于相位匹配条件，有效地将SMF中的基模耦合到GI-FMF中所需的OAM模式。同时，GI-FMF打破了所需本征模式与相邻矢量模式之间的简并性，从而使选择性激发的OAM模式得以保存和传输。作为原理验证，我们实现了一个工作在|l| = 1的稳定OAM模式下的全光纤器件。实验结果表明，OAM光束能够稳定传输，模式纯度约为95%，带宽为100 nm。这种全光纤器件可能有助于宽带宽OAM模式分割复用应用的进一步发展。
