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=Volume 8 - 2020

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=A unique orbital angular momentum (OAM) optical amplifier based on 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 by using the method of modified chemical vapor deposition. The cross-sectional microscope image of the fiber is obtained, and the difference in the refractive index between the ring core and the cladding of the fiber, measured by a three-dimensional refractive-index tester, reached 1%. The content of sulfur and lead in the ring core of the PbS-doped ring-core fiber is confirmed by energy spectrum analysis. The first order OAM optical amplifier based on PbS-doped ring-core fiber is built. 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 mode at 1550 nm. Its fluorescence spectrum ranges from 1100 to 1600 nm using the backward pumping method.