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 combination with the 400 mm, 0.46 NA pump cladding design, these fibers are ideal candidates for high power laser and amplifier applications. In addition, the core & pedestal waveguide design are specifically tailored to offer improved single-mode beam quality via efficient higher-order mode suppression while ensuring highly reliable splicing and easy handling and cleaving. Both fibers feature a 25 µm core (0.09 NA) and a 400 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 LMA-TDF-25P/400-M fiber is compatible with the NuMATCH passive fiber family offering unique compatibility performances at 2 µm. The fiber design is also available in polarization maintaining design (PLMA-TDF-25P/400-HE).