单模-多模光纤产生系列Bottle beam

提出一种利用多模光纤的多模干涉效应在自由空间中获得多个局域空心光（Bottle beam）的新方法。单模-多模光纤结构是一段多模光纤无偏心地连接到一段单模光纤上,光由单模光纤传输到多模光纤激发产生一系列的LP0，n 模,由于多模干涉效应在多模光纤中相互叠加，当入射到自由空间后形成了多个Bottle beam。文中对光束传输过程进行理论分析并利用Matlab 进行仿真实验, 结果表明在自由空间中可以获得系列Bottle beam。当多模光纤纤芯直径分别为45 m，60 m 和90 m 时所选择的光场段内的Bottle beam 的尺寸大小基本相同（约400 m20 m），而第一个空间暗域沿轴向两侧相对光强差值分别为0.62，0.41 和0.11，可见当多模光纤的纤芯直径越大时所得到的Bottle beam 暗域的轴向两侧光强越相近,因此也越有利于囚禁微粒。

Generate multi-Bottle beam using the structure of single mode fiber-multi mode fiber

A novel method for generating muti-Bottle beam based on the property of multimode interference in multimode fiber was proposed. The structure of single mode fiber-multi mode fiber was a multi-mode fiber (MMF) spliced onto a piece of single-mode fiber (SMF). When input field propagated to MMF, only linearly polarized (LP0,n) modes were excited. As a consequence of the superposition of multimode interference, multi-Bottle beam can be generated at certain axial regions in free space. In this paper, the theory of propagation process was analyzed and numerically simulated using Matlab software. The result indicates that the size of multi-Bottle beam about 400 m20 m can be obtained in free space. 45 m, 60 m, 90 m diameter MMF are selected, the size of Bottle beams obtained from them are almost the same, but both side relative intensity of axial region of dark space are 0.62, 0.41, 0.11 respectively. Therefore, the larger diameter of MMF, the more similar intensity is on both side of dark spot. It can work better for trapping particles.