%A Xu,Lingmin %A Shang,Yana %A Yang,Jinhong %A Chen,Zhenyi %A Pang,Fufei %A Liu,Huanhuan %A Dong,Yanhua %A Chen,Na %A Wen,Jianxiang %A Wang,Tingyun %D 2020 %J Frontiers in Physics %C %F %G English %K Optical fiber amplifier,PbS-doped ring-core fiber,orbital angular momentum (OAM),On-off gain,Fluorescence properties %Q %R 10.3389/fphy.2020.00198 %W %L %N 198 %M %P %7 %8 2020-June-03 %9 Original Research %# %! PbS-doped fiber amplifier for OAM %* %< %T Orbital Angular Momentum Optical Amplifier Based on PbS-Doped Ring-Core Fiber %U https://www.frontiersin.org/article/10.3389/fphy.2020.00198 %V 8 %0 JOURNAL ARTICLE %@ 2296-424X %X A unique orbital angular momentum (OAM) optical amplifier based on a ring-core fiber doped with lead sulfide (PbS) is realized for the first time in this study. The PbS-doped ring-core fiber is fabricated using the modified chemical vapor deposition method. The cross-sectional microscope image of the fiber is obtained. The difference in the refractive index between the ring core and the fiber cladding measured by a three-dimensional refractive index tester reaches 1%. The sulfur and lead content in the ring-core of the PbS-doped ring-core fiber is confirmed by energy spectrum analysis. A first-order OAM optical amplifier is built based on the PbS-doped ring-core fiber. The experiment confirms that the air-hole PbS-doped ring-core fiber can support the OAM |l| = 1 modes. In addition, 2.3 dB of on–off gain is obtained for the OAM |l| = 1 modes at 1,550 nm. The fluorescence spectrum obtained using the backward pumping method ranges from 1,100 to 1,600 nm.