Lasing Characteristics of Tm³⁺:Ho³⁺ Codoped Silica Fibre Laser Pumped by 1.18-μm Raman Fibre Laser

The fundamental characteristics of Fabry--Perot-cavity continuous-wave Tm--Ho codoped silica fibre lasers pumped by a 1.18 μm Raman fibre laser are presented. A maximum output power of 930 mW at 1880nm is generated for a fibre length of 1 m from the transition of Tm³⁺, with a slope efficiency of 32.4%. For a 3-m-long fibre, the maximum output power decreases to 650 mW at 1960 nm due to the laser emission from Ho³⁺ with a lower slope efficiency of 25%, which clearly shows the effective energy transfer from Tm³⁺ to Ho³⁺. The wavelength red-shifting of the laser emission originates from the transition competition and the emission cross section difference between Tm³⁺ and Ho³⁺.