Theoretical analysis of the dynamic behavior of highly-efficient erbium/ytterbium codoped fiber lasers

A numerical study of the transient behavior of single-mode Er/sup 3+//Yb/sup 3+/ codoped fiber lasers is presented. The model, based on propagation-rate equations, includes both uniform up-conversion from the /sup 4/I/sub 15/2/ and /sup 4/I/sub 9/2/ erbium levels and the pair-induced energy transfer process from ytterbium to erbium. We show that neglecting the r dependence of the operating fiber laser parameters allows accurate simulation results at minimum numerical effort. Using this numerical model, we characterize the laser relaxation oscillations and the effect of ytterbium on the dynamic behavior and stability with respect to fluctuations of the pump power. Our results confirm that the presence of Yb/sup 3+/ enhances the efficiency of the laser and show that its stability is also significantly improved.