Klenke, A.A.KlenkeSteinkopff, A.A.SteinkopffAleshire, C.C.AleshireJauregui, C.C.JaureguiKuhn, S.S.KuhnNold, J.J.NoldHaarlammert, N.N.HaarlammertSchreiber, T.T.SchreiberTünnermann, A.A.TünnermannLimpert, J.J.Limpert2022-05-062022-05-062021https://publica.fraunhofer.de/handle/publica/41689210.1109/CLEO/Europe-EQEC52157.2021.9541953Multicore fibers have the potential to combine the advantages of optical fibers (such as their high average power capability, high efficiency and well-defined beam quality) with those stemming from the large beam areas commonly used in other laser architectures. Coherent combination can then be employed to achieve one single, high-quality, output beam [1] , [2]. To match and even surpass the performance of state-of-the-art lasers systems comprising multiple separate fiber amplifiers, multicore fibers need to leverage the same technological advancements. One example is the use of a rod-type geometry with large core diameters to mitigate detrimental nonlinear effects. In this contribution, we present our high power laser results achieved with an in-house, all-glass, rod-type multicore fiber, whose basic structure is shown in figure 1. The fiber contains 16 ytterbium-doped cores in a rectangular arrangement with a diameter of 22m each, operating at near single-mode output. The core-to-core pitch is 58m. An embedded octagonal fluoride ring is used as the guiding mechanism for the pump with a diameter of 310m and a NA of 0.22. A device length of 1.1 m was chosen to provide sufficient pump absorption.en620conference paper