Numerical analysis of mode competition and selection in Yb-doped multicore fiber lasers

Abstract

In this paper, we present an analysis of transverse mode competition mechanism in multicore fiber lasers based on the transversally-resolved steady rate equations with consideration of transverse gain distribution and mode propagation loss. Based on the model, the output beam properties of 7-core and 19-core fiber lasers are simulated numerically when applying a plane reflection mirror and Talbot cavity as the feedback boundary conditions, respectively. We propose a new parameter of brightness factor to find out the best Talbot distance. We also give analysis on the influence of the fiber core separation distance and core diameter to the output laser beam quality. The study shows that the Talbot cavity can realize the mode selection of multicore fiber lasers and make the in-phase supermode dominate in the output beam, thus enhancing the quality of the output beam. The shorter the core separation distance and the core diameter are, the better the output beam quality would be. The best optimized core separation distance within acceptable beam quality restriction and the processing technic limit is obtained. This work has great prospective in the design and application of multicore fibers.