Multiple core modes conversion using helical long-period fiber gratings

Chen Jiang, Kaiming Zhou, Bing Sun, Ying Wan, Yuehui Ma, Zhiqiang Wang, Zuxing Zhang, Chengbo Mou, Yunqi Liu

Research output: Contribution to journalArticlepeer-review


We propose and demonstrate the fabrication of an all-fiber mode converter enabling simultaneous generation of multiple high-order core modes, which is realized by inscribing a helical long-period grating (HLPG) in a few-mode fiber (FMF) using a femtosecond laser. Helical refractive index modulation is introduced by continuously irradiating the core region with a highly focused femtosecond laser, while the fiber moves in a spiral path through a three-dimensional translation stage. Mode conversion from the LP01 mode to high-order core modes, including LP11, LP21, LP31, LP02, LP12, and LP41 modes, is achieved by controlling the inscription pitch of the grating. Moreover, first-, second-, third-, and fourth-order orbital angular momentum (OAM) modes can be directly generated using the HLPGs, and multiple OAM modes of different topological charges can be simultaneously excited using a single high diffraction order HLPG. This approach offers a new option for implementing with high-integration high-order mode converters or OAM mode generators.
Original languageEnglish
Pages (from-to)2965-2968
Number of pages4
JournalOptics Letters
Issue number11
Early online date25 May 2023
Publication statusPublished - 1 Jun 2023


  • Atomic and Molecular Physics, and Optics


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