Chinese Optics Letters, Vol. 18, Issue 2, 020602 (2020)
Highly efficient excitation of LP01 mode in ring-core fibers by tapering for optimizing OAM generation
Chunxiang Zhang, Fufei Pang, Huanhuan Liu, Lifei Chen, Junfeng Yang, Jianxiang Wen, and Tingyun Wang*
- Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Joint International Research Laboratory of Specialty Fiber Optics and Advanced Communication, Shanghai Institute for Advanced Communication and Data Science, Shanghai University, Shanghai 200444, China
We have demonstrated the highly efficient excitation of the linearly polarized mode (LP01) in ring-core fibers (RCFs) by tapering the spliced point between the RCF and the standard single-mode fiber (SMF) to optimize all-fiber orbital angular momentum (OAM) generation. The tapering technique has been investigated theoretically and experimentally. Before tapering, only 50% of light can be coupled from SMFs to RCFs. The modal interference spectrum with an extinction ratio (ER) of ～9 dB is observed, showing that higher-order modes are excited in RCF. By tapering the spliced point, 90% of light is coupled, and the ER is minimized to be ～2 dB, indicating that the higher-order modes are effectively suppressed by tapering. Such tapered spliced points of RCF–SMF are further applied for all-fiber OAM generation. The efficiencies of OAM+1 and OAM?1 generation are found to be enhanced by approximately 11.66% and 12.41%, respectively, showing that the tapered spliced point of the RCF–SMF is a feasible way to optimize OAM generation.