Research On Key Technologies Of Multi-core Double-clad Fiber Laser

:Fiber lasers have lots of advantages such as small volume, light weight,, good beam quality, high thermal efficiency, high conversion efficiency, and low threshold. So nowadays it become the important research area in laser field. However, the further improvement of out power is limited in the single core fiber laser due to the existence of thermal effects, nonlinear effects,optical damage and other restrictive physical mechanism in doped fibers. Currently the primary mean to access high-power laser beam is the combination of coherent beam combining technology and cladding-pumped fiber laser technology. In this dissertation, we focus on the research on multi-core self-assembly coherent beam combining method in order to satisfy the requirement of the development of high power laser. Main research contents are listed as below.Firstly, a diffraction model was established for modeling multi-core self-assembly coherent beam combining method,.The effect of some parameters, such as core diameter, distance between adjacent cores,core number,and so on, on the result of combining beam are discussed in detail. Numerical results demonstrate that the output power of multicore self-assembly coherent beam combining method can be improved by increasing the diameter of single core, decreasing the distance between the adjacent cores and increasing core number under the assumption that the output power of single core keep constant. It will be helpful for the qulity of the combined beam by reducing the wavelength and diffraction length without considering the cavity length.Secondly, the impacts of different core arrangements on the quality of combining-beam are studied,and the optimum scheme of the core array is deduced. Through comparing the effects of combining beam of single-ring array, multi-ring array,square lattice array and hexagonal lattice array, single ring array is the optimum array which can obtian the good effects of combining beam.In order to improve the utilization ratio of the inner cladding cross-section, multi-ring arrangement can be used, but cores should be arranged in rings as few as possible.In addition,some unfavorable factors exsisted in fibers such as thermal effects, divergence angle and so on.First assumed light field in a single core is Gaussian distribution,and analysissed combined beam with different Gaussian parameters. Second,this paper analysised and simulated divergence angle with different optical parameters. What’s more through the study of heat conduction equation, this paper gave out one methord to solve the fiber temperature distribution. It can be found that thermal effects and nonlinear effects can be effectively reduced by choosing the rational design parameters of multi-core optical fiber and fiber grating,using appropriate pump mode,adjunction of cooling device and some optimization device.The above results provide a useful reference for further study of higher-power fiber lasers.