Backreflection of the residual pump power into the cavity, and optimization of the fiber length, may significantly improve the efficiency of a strongly pumped fiber laser. A rate equation model is introduced and studied. Examples for Yb3+-doped fiber lasers, with DBR mirrors at either end, show that employing such a geometry results in higher efficiency with shorter optimal fiber length. Approximate analytical and quasi-analytical expressions are shown to be in excellent agreement with the exact numerical solution of the rate equations.
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