Research On Bending Resistant Large Mode Area Few-mode Segmented Cladding Fiber

With the rapid development of lasers,increasing demands on the output power has been put forward.Fiber lasers have higher output power than conventional lasers.However,the nonlinear effects and mode instability in fiber lasers impair the beam quality of the fiber laser.Large mode area fiber has been widely concerned because of its low loss and resistance to bending,which can effectively improve the output beam quality of the fiber laser and increase the threshold power of the laser.This paper mainly studies and designs anti-bending large mode area fiber to improve the performance of fiber laser.Based on the finite element method,this paper makes simulation analysis based on the finite element simulation.Through analyzing the results,the performance of SCF and FHC-SCF is studied in depth,and a new large mode area fiber is innovatively designed.The main work and innovative achievements of this paper are as follows:(1)The bending characteristics and the mode area of the SCF fiber are analyzed with the variation of the parameters of the segmented cladding fiber,and the structure of the segmented cladding fiber is optimized.When the core radius is 20?m and the bending radius is 15 cm,the mode area of the segmented cladding fiber is 817 ?m2.The loss ratio between minimum high-order mode loss and fundamental mode of the fiber is 38,with good single mode property and large mode area.(2)The structure of FHC-SCF is analyzed.The bending characteristics and the mode area are analyzed with the variation of the parameters of the FHC-SCF.The structure of FHC-SCF is optimized.When the fiber core radius is 20?m and the bending radius is 15 cm,the mode field area is 804?m2 and loss ratio between minimum high-order mode loss and fundamental mode is 40.(3)TA-FSCF is proposed and compared with the performance of the SCF and FHC-SCF.Compared with SCF,when the loss ratio between minimum high-order mode loss and fundamental mode of the TA-FSCF is close to that of SCF,the mode area of the TA-FSCF is larger than that of the SCF.Compared with FHC-SCF,the mode field area and the loss ratio between minimum high-order mode loss and the mode area of TA-FSCF are both greater than those of the FHC-SCF.The performance of TA-FSCF is completely better than FHC-SCF.(4)The bending performance of the TA-FSCF and the mode area of the fundamental mode are analyzed.The TA-FSCF's structure parameters are optimized,and design performance is relatively balanced.By studying bending resistant large mode area fiber and optimizing the fiber structure,the fiber with good single mode property and large mode area is designed,which provides a good foundation and guidance for the high power output of fiber laser.