Experimental Investigation of Tm³⁺-Doped Silica Double-Cladding Fibre Laser

Using a Tm³⁺-doped double-cladding silica fibre, we produce a maximum cw 2.2W output at approximately 2μm. The highest achieved slope efficiency is 29.3% respect to the launched pump power. The lowest threshold is 1.85W using the double pass pump method with the fibre length 2.7m, which is the lowest reported threshold of cladding pump of the ³⁺H₄ level. The fibre laser output peak wavelength ranges from 1.967μm to 2.018μm with cavity 1 (R₁=1 and R₂=0.04) and from 1.95μm to 1.99μm with cavity 2 (R₁=0.04 and R₂=0.04), as the fibre length varies.