Experimental Investigation of Tm 3+ -Doped Silica Double-Cladding Fibre Laser

Using a Tm 3+ -doped double-cladding silica fibre, we produce a maximum cw 2.2 W output at approximately 2 μm. The highest achieved slope efficiency is 29.3% respect to the launched pump power. The lowest threshold is 1.85 W using the double pass pump method with the fibre length 2.7 m, which is the lowest reported threshold of cladding pump of the 3 H 4 level. The fibre laser output peak wavelength ranges from 1.967 μm to 2.018 μm with cavity 1 ( R 1 = 1 and R 2 = 0.04) and from 1.95 μm to 1.99 μm with cavity 2 ( R 1 = 0.04 and R 2 = 0.04), as the fibre length varies.