Model and Characteristics of Self-Pulsing in ${\rm Tm}^{3+}$ -Doped Silica Fiber Lasers

In this paper, a theoretical model, taking into account the phonon-assisted excited-state absorption process (³H₅ →³H₄), has been constructed to explain the self-pulsing (SP) phenomenon in the Tm³⁺-doped fiber lasers. Both numerical simulation and experimental investigation on the SP characteristics of ~2-μ.m Tm³⁺-doped fiber lasers have been carried out. The numerical simulation shows agreement with the experimental results. Furthermore, the impacts of output coupling, pump intensity, and Tm³⁺-ion doping concentration on the SP characteristics of the Tm³⁺-doped fiber lasers have been studied explicitly, and optimization of the SP features has been discussed. In addition, the potential applications of SP in fiber lasers or solid-state lasers have also been proposed.