Multicore Fiber Lasers with fs-inscribed Grating Arrays: Recent Developments and Perspectives

The technology of point-by-point refractive index modification by femtosecond (fs) laser enables fiber Bragg gratings (FBGs) inscription at arbitrary position in the fiber core (both in longitudinal and transverse direction) that offers new opportunities for development of advanced multimode and multicore fiber lasers. Here we review our recent results on the point-by-point fs inscription technology development for fabrication of FBG arrays in passive and active multicore fibers and their application as complex reflectors of Raman and Yb-doped multicore fiber (MCF) laser cavities. We demonstrate new opportunities of tailoring spatial and spectral characteristics of the MCF lasers with an emphasis on intracavity beam combination with single beam output and laser spectrum narrowing offering efficient extra-cavity combination. Perspectives of FBGs/arrays fabrication with the use of spatial light modulator are discussed.