Modal Properties of Yb-Doped 4-Core Fibers under Heat Load

Multicore fibers, which incorporate a number of amplifying cores in a single fiber, represent a possible solution to overcome the current power limit of short-pulsed fiber-based lasers [1,2], which is related to dynamic thermo-optic instabilities, caused by the unwanted presence of higher-order modes [3]. However, the effects of thermo-optic perturbations on the guiding properties of multicore fibers should be carefully taken into account, as it has been recently demonstrated for dual-core fibers [4]. In particular, it has been shown that the impact of the heat load applied to the cores on the behaviour of fundamental and higher-order supermodes (SMs) strongly depends on the core separation, that is on the coupling strength between cores [4].