Transverse mode competition in gain-guided index antiguided fiber lasers

Single-mode laser action has been reported previously in a gain-guided, index antiguided fiber using a scalable side pumping scheme. In this paper we demonstrate the role of transverse mode competition on laser oscillation in such a fiber laser. It enables single, lowest-order mode lasing with a beam quality of M2<2 when using a combination of large fiber core radius and low output coupler reflectivity previously considered to rule out gain-guided index antiguided lasing with such beam quality. In addition, the larger core radii fibers and low output coupler reflectivity enables improved slope efficiency. Both theoretical analysis and experimental results are presented demonstrating mode competition governed lasing in a gain-guided, index antiguided fiber.