Coherent introduces the newest series of large-mode area, high efficiency Thulium-doped double clad fibers inspired from the most recent advances in thulium-doped technology. The glass composition is improved to maximize the cross-relaxation process in order to achieve 2 mm efficiencies around 60% and higher when pumping at ~793 nm. In addition, the waveguide design is specifically tailored to offer improved beam quality. The pedestal layer surrounding the core is optimized to guarantee efficient higher-order mode suppression and high beam quality while ensuring highly reliable splicing and easy handling and cleaving. Both fibers feature a 25 µm core (0.09 NA) and a 250 µm clad diameter allowing for a large mode field diameter and short device lengths thereby minimizing non-linear effects such as SBS and SRS. The - M fiber is compatible with the NuMATCH passive fiber family offering unique compatibility performances.in the higher 2 µm wavelength gain spectrum. The -LC fiber features a lower concentration Tm-concentration best suited to operate in the shorter wavelength region of the 2 mm gain spectrum.