Research On Power Alignment Technology Of High Power Fiber Laser Fiber Fusion

In order to improve the splice quality of double-cladding fiber in high power fiber lasers and solve the problems of optical-to-optical conversion efficiency is degraded and he beam quality is deteriorated of the laser caused by core misalignment at the fusion point.Optical power alignment technology of the double-cladding fiber is studied.Based on classical wave theory and mode propagation theory,the relationship between the core misalignment and coupling efficiency was analyzed theoretically when there are basic-mode light or higher-order mode light in the core.Building the power alignment system with the nufern 20/400 large-mode-area double-cladding fiber to study the light source and mode field adaptation of the system experimentally.And the influence of the high-order mode on the relationship between core misalignment and coupling efficiency was verified.It was indicated that the sensitivity of the coupling efficiency to the core dislocation is reduced when there are the higher-order mode light exist in the fibers.According to the above study,the power alignment system of double-cladding fiber is optimized,and the alignment accuracy of double-cladding fiber is improved.The effect of fiber core misalignment on the beam quality of double-cladding fiber is studied theoretically.For the problem that the model coupling process is not obvious and computational complexity exists in classical wave model,a model-field coupled tracking model is proposed.The coupling process of mode field is represented by Gaussian deformation that calculate the M2 in different core misalignment.The relationship between the M2 of the 20/400 large-mode-area double-cladding fiber and the core misalignment is also measured,the measured results agree well with the theoretical model.It can calculate the beam quality in different core misalignment using the mode-field coupling tracking model more efficientlyThe alignment system of double-cladding fiber is used to study the relationship between the splice parameters and the quality of the splice points,find the best splice parameters to make the quality of splice points best.KW-level double-end pumped high power fiber laser system is successfully constructed with this system.The optical-to-optical conversion efficiency is more than 73%and the beam quality is better than 1.22,which achieves the output of quasi-single-mode.