Wavelength Tunable Orbital Angular Momentum Mode Convertor Based on Helical Long-Period Grating Inscribed in Six-Mode Fiber Using CO2 Laser

Weidong Zhang,Long Chen,Yunqi Liu,Chen Jiang,Xinyi Zhao,Yuehui Ma

doi:10.1109/jsen.2023.3285072

Abstract

We demonstrated the fabrication of orbital angular momentum (OAM) mode convertors (MCs) operating at 1.3 μm to 2.1 μm waveband based on the helical long-period gratings (HLPGs) inscribed in the few-mode fiber (FMF) using a CO 2 laser. The ±1 st , ±2 nd , and ±3 rd OAM mode can be directly generated by the HLPGs with efficiencies of more than 90%. The torsion sensitivities of 1 st , 2 nd and 3 rd order OAM modes in 2 μm waveband are 0.52 nm/(rad/m), 0.55 nm/(rad/m) and 0.36 nm/(rad/m), which has increased by 5.8 times, 2.8 times, and 1.6 times compared to that in 1.3 μm waveband, respectively. The strain sensitivities of 1 st , 2 nd and 3 rd order OAM modes in 2 μm waveband are - 4.2 pm/με、 - 4.0 pm/με and - 4.9 pm/με, which has increased by 2.3 times, 2 times, and 2.2 times compared to that in 1.3 μm waveband, respectively. The proposed OAM mode MCs based on the HLPGs can function as not only promotion of optical communication system but also high torsion sensitivity sensors in the sensing field.

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