Yin Guolu, Liang Chuancan, Ikechukwu Iroegbu Paul, Deng Ming, Shi Leilei, Fu QingJiang, Zhu Tao, Zhang Lin
Opt Lett. 2019 Feb 15;44(4):999-1002. doi: 10.1364/OL.44.000999.
In this Letter, we demonstrate, to the best of our knowledge, a novel method to generate an orbital angular momentum (OAM) based on the principle of the modal interference in a two-mode fiber. At the interference dips, the left- or right-handed circular polarized HE modes can be ideally converted into the ±1-order OAM beam. To verify this concept, we employed the femtosecond laser micro-processing technology to write micro-waveguides in the two-mode fiber and hence realized the in-line modal interferometer. To enhance the mode conversion efficiency at the dips, we optimized the waveguide parameters both theoretically and experimentally. The interference spectrum and spiral/fork patterns confirm the OAM beam generation with an efficiency as high as 99%.
在本信函中，据我们所知，我们展示了一种基于双模光纤中模式干涉原理产生轨道角动量（OAM）的新方法。在干涉凹陷处，左旋或右旋圆偏振HE模式可理想地转换为±1阶OAM光束。为验证这一概念，我们采用飞秒激光微加工技术在双模光纤中写入微波导，从而实现了在线模式干涉仪。为提高凹陷处的模式转换效率，我们在理论和实验上对波导参数进行了优化。干涉光谱和螺旋/叉状图案证实了OAM光束的产生，效率高达99%。
