Fabrication and properties of domestic long tapered ytterbium-doped fiber with high tapering ratio

A ytterbium-doped large-mode-area step-index fiber perform was fabricated by chelate precursor doping technique. For the purpose of raising the threshold of nonlinear effects and transverse mode instability simultaneously, a long tapered fiber was drew by changing the perform drawing speed. The core/cladding diameter of this tapered fiber was varied from 10/155 to 26/400 μm in 18m-long with the tapering ratio of 2.6. Using this fiber as a gain medium for a fiber laser in amplifier, the beam quality factor M2 was ~1.2 when the output power obtained over 1.2kW with slope efficiency of 74.5%. The laser output spectrum was centered at 1063.8nm with narrow 3dB bandwidth of 0.26nm. The stimulated Raman scattering suppression ratio was about ~34.7dB.