Mode competition in concentric-type multicore fiber lasers combined with large mode area single mode fiber

Abstract

The mode competition mechanism in concentric 4-core and 7-core fiber lasers with large mode area single mode (SM) fiber as in-phase supermode selection component is presented. The coupling coefficient between the fundamental mode in large mode area SM fiber and each supermode in mutlicore fiber is discussed. For individual supermode in multicore fiber, the coupling coefficient is optimized as a function of the core radius of SM fiber as well as the distance between multicore fiber and SM fiber. The optimization results demonstrate that only two supermodes are involved in concentric-type fiber lasing - in-phase and anti-phase supermode, owing to the negligible coupling coefficients of the other supermodes. Furthermore, to achieve the best in-phase supermode selection, the core radius of SM fiber will be optimized for maximum coupling coefficient difference between in-phase supermode and anti-phase supermodes. The numerical results illustrate that in-phase supermode always dominate the output and is the highest when the distance equals zero. Compared to conventional multicore fiber lasers with Talbot cavity, this all-fiber configuration based on large mode area SM fiber has higher-order supermodes more efficiently suppressed and high-brightness output may be achieved.