High-power very large mode-area thulium-doped fiber laser

Large-pitch photonic-crystal fibers have demonstrated their unique capability of combining very large mode areas, high output powers and robust single-mode operation at a wavelength of 1 µm. In this Letter, we present the experimental realization of thulium-doped very large mode-area fibers based on the large-pitch fibers with record mode-field diameters exceeding 60 µm and delivering more than 52 W of output power