High-order OAM mode generation in a helical long-period fiber grating inscribed by an oxyhydrogen-flame

Abstract

In this study, an all-fiber ±3-order orbital angular momentum (OAM) mode generator with ∼90% conversion efficiency is proposed and experimentally demonstrated. By using a helical long-period fiber grating (HLPFG) inscribed by an oxyhydrogen-flame, the fundamental mode (LP01) of the six-mode fiber (6MF) can be effectively converted into the OAM±3 mode without the need for polarization control. This is the first demonstration of the all-fiber ±3-order OAM mode generator by an oxyhydrogen-flame-induced HLPFG approach as far as we know. In addition, the broadband tunability of the ±3-order OAM mode generator within 1520–1630 nm is demonstrated just by changing the pitch of the helical grating. We believe that the proposed tunable ±3-order OAM mode generator can offer a new alternative for high-order OAM mode generation.