All-fiber second-order optical vortex generation based on strong modulated long-period grating in a four-mode fiber

Hang Wu; Shecheng Gao; Bingsen Huang; Yuanhua Feng; Xincheng Huang; Weiping Liu; Zhaohui Li

doi:10.1364/OL.42.005210

All-fiber second-order optical vortex generation based on strong modulated long-period grating in a four-mode fiber

Opt Lett. 2017 Dec 15;42(24):5210-5213. doi: 10.1364/OL.42.005210.

Authors

Hang Wu, Shecheng Gao, Bingsen Huang, Yuanhua Feng, Xincheng Huang, Weiping Liu, Zhaohui Li

PMID: 29240174
DOI: 10.1364/OL.42.005210

Abstract

We propose an effective all-fiber method to generate a high-order optical vortex (OV) via twisting a strong modulated long-period fiber grating (LPFG) written in a four-mode fiber (4MF). With a special design and optimization of the procedures of CO₂-laser irradiation, an LPFG with strong period deformation is achieved in the 4MF. Based on this LPFG, we can directly convert the linear polarization (LP) fiber fundamental mode (LP₀₁) to the high-order LP core mode (LP₂₁) with efficiency of 99.7% and then transform the LP₂₁ mode into a high-order OV mode (±2 order). This is the first time, to the best of our knowledge, that ±2-order OV modes have been experimentally generated with just one fiber grating in an all-fiber-system.