Study On Effect Of Bending Stress On Laser-induced Damage Threshold

As the loading medium of laser,optical fiber has been widely used due to its simple manufacture and low price.As a product of the combination of fiber and laser technology,high-power fiber lasers have attracted a lot of attention from academia and industry since their inception.The first problem that high-power optical fibers need to face is that the optical fiber is prone to laser damage due to its own fragility,and the bending stress,as an inevitable existence in the laser transmission process,will affect the laser damage characteristics of the optical fiber.Therefore,in order to explore the phenomenon of fiber bending-induced laser damage and provide guidance for the experiment of fiber laser damage from the theoretical level,the main research work of this paper is as follows:(1)Fiber structure design and bending model construction.The design of optical fiber transmission model and the model construction of various structural optical fibers are completed through the setting of physical structure parameters.Considering the change of the bending stress on the properties of the fiber,on the basis of the existing multi-structural fiber models,the fiber bending model is constructed by analyzing the influence of the bending stress on the refractive index.(2)Research on the effect of bending stress on the electric field distribution of optical fiber.Based on the finite element numerical simulation theory,the model analysis of the optical fiber model is completed by constructing the corresponding wave optics equations.Based on the mode analysis results,the electric field distribution of the optical fiber transmission is calculated,and the influence of bending on the electric field distribution of the optical fiber is analyzed.Studies have shown that under the action of bending stress,the electric field distribution of the optical fiber will show a non-uniform distribution state.(3)Research on the relationship between bending stress and laser damage.Based on the analysis results of the fiber electric field distribution,combined with the fiber laser damage formula,the change of the fiber laser damage threshold under the bending stress is calculated,and the research on the influence of the fiber damage threshold of various optical fibers under the bending stress is completed.Studies have shown that most optical fibers are prone to laser damage due to the influence of bending stress,and the magnitude of bending stress is positively correlated with the degree of laser damage.Based on the finite element method,this paper combines the bending stress and fiber laser damage theory for simulation research,analyzes the fiber laser damage phenomenon,and determines the influencing factors of fiber laser damage.Our research helps to improve the understanding of the damage mechanism of fiber lasers,and provides theoretical support and assistance for broadening the application fields of high-power lasers.