Supermode lasing and light amplification in multicore bismuth-doped fiber

Multicore fibers are promising structures with specific light propagation properties, which can be managed to benefit several applications in optical communications, fiber lasers and amplifiers, high-resolution imaging, and fiber-based sensors. The current use of multicore fibers in laser technology is mainly focused on in-phase coherent beam combining in far-field regions (out-cavity) using bulk optical elements. However, this approach is challenging in terms of the power scalability of all-fiber lasers (intra-cavity), particularly with using low-gain media, where it is needed to provide mode-coupling (supermode propagation) stability along relatively long lengths. Here, we report a conceptual design and fabrication of a multicore bismuth-doped fiber that is capable of achieving light amplification and stable lasing in the E-telecom band inside the cavity using the supermode selection approach. By analysis of experimental and simulation data, it was found that the employment of the proposed design of a Bi-doped fiber provides a considerable advantage over the single-core fiber in terms of laser performance (output power, slope efficiency) in the cladding-pumped configuration. These results open up new opportunities for further advancement of the optical fiber technology towards efficient bismuth-doped fiber-integrated amplifiers and lasers for the O+E+S+C+L+U-telecom bands, which may find important applications, especially for the development of next-generation multiband optical transmission systems.