Efficiency of Tm3+ -doped silica triple clad fiber laser

We present measurements of the slope efficiency and the pump power at threshold of a Tm3+ -doped silica triple clad fiber laser emitting at 2.02 μm using different cooling techniques. The slope efficiency of 53.6 % was obtained at a temperature of 25oC with a maximum output power of 5 W for 19 W of absorbed power at the pump wavelength of 800 nm and 9.9 W threshold. In a slightly different setup, the output power could be increased to 10 W for an absorbed pump power of 32 W.