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

The continuous wave operations of highly-efficient Er/sup 3+//Yb/sup 3+/ co-doped fiber lasers pumped at 980 nm are numerically analyzed. The model, based on propagation-rate equations, includes uniform upconversion from the /sup 4/I/sub 13/2/ and /sup 4/I/sub 11/2/ erbium levels and a pair-induced energy transfer process from Yb/sup 3+/ to Er/sup 3+/; 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.