Low-loss and helical-phase-dependent selective excitation of high-order orbital angular momentum modes in a twisted ring-core fiber

We propose a method for the selective generation of high-order orbital angular momentum (OAM) modes by twisting a ring-core fiber (RCF). Theoretically, 22 OAM modes can be generated in the twisted RCF with effective mode separation. We experimentally demonstrate the excitation of OAM modes up to the fourth order. The positive or negative topological charge is determined by the clockwise or counter-clockwise twist direction, indicating that the helical phase of the OAM can be controlled by the twist orientation. Compared with other fiber-based methods, the high-order OAM modes generated by our approach have the characteristics of low loss (minimum 0.3 dB), high mode purity (maximum 98%), and simple fabrication. This has potential applications in high-resolution imaging, high-capacity fiber-optics communication, vortex-optics sensing, and other fields. (C) 2022 Optica Publishing Group

Automated summary

We propose a method for selectively generating high-order orbital angular momentum (OAM) modes using a twisted ring-core fiber (RCF). Experimental results demonstrate the excitation of OAM modes up to the fourth order, indicating that the twist direction can control the helical phase of the modes. Compared with other methods, this approach has the advantages of low loss, high mode purity, and simple fabrication.