AUTHOR=Xu Lingmin , Shang Yana , Yang Jinhong , Chen Zhenyi , Pang Fufei , Liu Huanhuan , Dong Yanhua , Chen Na , Wen Jianxiang , Wang Tingyun 

TITLE=Orbital Angular Momentum Optical Amplifier Based on PbS-Doped Ring-Core Fiber

JOURNAL=Frontiers in Physics

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2020.00198

DOI=10.3389/fphy.2020.00198

ISSN=2296-424X

ABSTRACT=<p>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 |<italic>l</italic>| = 1 modes. In addition, 2.3 dB of on–off gain is obtained for the OAM |<italic>l</italic>| = 1 modes at 1,550 nm. The fluorescence spectrum obtained using the backward pumping method ranges from 1,100 to 1,600 nm.</p>