Study On The Supermode And In-Phase Locking In Multicore Fiber Lasers

Multicore fiber lasers have larger mode areas, resulting in higher power thresholds for nonlinear processes such as stimulated Raman scattering and stimulated Brillouin scattering. Because of longer distributed distance of the cores, thermal mechanical effects are decreased compared with those of single-core lasers. Therefore, multicore fiber lasers are proposed as a candidate for the power scaling. The progress of multicore fiber lasers is simply introduced. Optical fields propagating in multicore fibers are coupled evanescently, resulting in what are called supermodes. In this article, the coupled-mode theory for analyzing supermode of fiber transmission is introduced. By mean of the theory, assuming under weak-coupling conditions, the supermodes are approximated as linear superposition of modes of individual cores with appropriate coefficients. The near-field mode distributions of some supermodes are numerically calculated, and the corresponding mode distribution patterns are drawn. For making the multicore fiber laser preferentially operate in a particular supermode so that improving beam quality, an in-phase locking method based on self-imaging Talbot external cavity is introduced.