Theoretical modelling of dual-wavelength pumped Yb3+-Tm3+ co-doped silica fibre laser

Numerical simulations have, for the first time to our knowledge, been carried out to characterize the Yb3+-Tm3+ co-doped silica fibre laser (YTFL), defined by a fibre grating and an end mirror, by using the rate equations, which take into consideration both the energy transfer processes from Yb3+ to Tm3+ ions and the cross-relaxation processes among different Tm3+ ions. A dual-wavelength pumping scheme with one at 805 nm and the other at 975 nm is used to pump the YTFL. We have investigated the wavelength-dependent output power of the YTFL, from 1750 to 2200 nm, which takes its maximum output power at similar to 1800 nm. The effect of the cross-relaxation processes in the Tm3+-doped silica fibre laser has been studied. The results indicate that these processes are beneficial to the laser and should be considered in the theoretical modelling. The influence of the Yb3+ concentration on the characteristics of the YTFL has also been analysed and the results show that Yb3+ dopants can improve the output power and slope efficiency of the laser.