Tm³⁺-doped silica-glass fiber for ∼2-μm fiber laser

Tm³⁺-doped silica-glass preforms were fabricated by the modified chemical vapor deposition process combined with the solution doping technique. Its spectroscopic properties were evaluated according to the detected absorption spectrum and the fluorescence spectrum. The calculated maximum emission cross section of Tm³⁺ ions in this core glass is 5.66×10^-21  cm², and the tested fluorescence lifetime is 544 μs at 1816 nm. According to the theory of Dexter and Forster, the cross-relaxation rate was calculated by the integral overlap of the absorption and emission cross sections. A double-cladding fiber with a core NA of 0.14 was prepared by high temperature drawing. A maximum 14.5-W fiber laser output centered at 2001 nm with a slope efficiency of 50.6% was obtained from a 4.5-m-length double-cladding fiber.