Modeling of passively Q-switched Er/sup 3+//Yb/sup 3+/-codoped clad-pumped fiber lasers

We present the modeling of passively Q-switched Er/sup 3+//Yb/sup 3+/-codoped double-clad fiber lasers (EYDFL). Both two-level and three-level saturable absorbers (SAs) are used. The model is based on detailed rate equations of SAs, Er/sup 3+/, and Yb/sup 3+/ populations in the fiber, and light propagation equations including spontaneous emissions due to both Er/sup 3+/ and Yb/sup 3+/. Laser output characteristics including pulse energy, width, peak power, repetition frequency (PRF), and average power are computed as functions pump power, fiber length, single-mode/multi-mode fibers, Er/sup 3+//Yb/sup 3+/ concentrations, out-coupling reflectivity, focus area on the SA, and SA doping and length. Several transition metal-doped crystal SAs and semiconductor SA mirrors (SESAM) are considered and compared.