Modeling of highly-efficient grating-feedback and Fabry-Perot Er 3+-Yb3+ co-doped fiber lasers

The continuous wave operations of highly-efficient Er³⁺/Yb³⁺ co-doped fiber lasers pumped at 980 nm are numerically analyzed. The model, based on propagation-rate equations, includes uniform upconversion from the ⁴I_13/2 and ⁴I_11/2 erbium levels and a pair-induced energy transfer process from Yb³⁺ to Er³⁺; it allows the description of both single-mode and multimode laser operations. Numerical results show that slope efficiencies close to the quantum limit, with threshold pump powers of few mW, can be achieved in short single-frequency fiber lasers using grating Bragg reflectors. Moreover, we demonstrate the possibility of performing equispaced multiwavelength laser emissions in high-concentration Fabry-Perot fiber microlasers