Open AccessStudy on the adiabaticity criterion of the thermally-guided very-large-mode-area fiber
Author(s) -
Wenbo Liu,
Jianqiu Cao,
Jinbao Chen
Publication year - 2018
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.26.007852
Subject(s) - optics , cladding (metalworking) , adiabatic process , bent molecular geometry , optical fiber , materials science , refractive index , graded index fiber , single mode optical fiber , polarization maintaining optical fiber , double clad fiber , mode volume , fiber , physics , fiber optic sensor , thermodynamics , composite material
The adiabaticity criterion of the thermally-guided very-large-mode-area (TG VLMA) fiber is presented based on the mode-coupling theory firstly, to the best of our knowledge. The requirement for the adiabatic propagation of fundamental mode is discussed systematically. It is revealed that the pump absorption plays the most important role and the adiabaticity criterion can be met as long as it is small enough. Then, the effects of the configuration parameters of TG VLMA fiber on the up-limitation of pump absorption for the adiabaticity criterion are investigated. It is found that for the straight TG VLMA fiber, reducing the initial refraction index and inner-cladding diameter and utilizing the bi-directional pumping scheme are beneficial to the adiabatic propagation of fundamental mode. The bent TG VLMA fiber is also studied. It is found that the bent fiber is much more difficult to meet the adiabaticity criterion than the straight one. The results show that even with the 100-cm bend radius, the pump absorption should be smaller than 1 dB/m to meet the adiabaticity criterion. It is suggested that enlarging the core-to-cladding ratio can be helpful for loosening the adiabaticity criterion of bent TG VLMA fiber. These pertinent results can provide significant guidance for understanding and designing the TG VLMA fiber and pertinent lasers and amplifiers.