Theoretical modeling of Tm-doped silica fiber lasers

The theoretically determined slope efficiency and threshold pump power for continuous wave (CW) operation of a Tm-doped silica fiber laser are presented. The associated rate equations are solved using standard techniques and, in conjunction with the published and our measured spectroscopic parameters as input, the model was used to examine the fiber laser output for a variety of fiber and pump configurations. After good agreement was achieved between the model calculations and the published experimental measurements, the model was used to examine the relative performance of the fiber laser when the pump wavelength was varied over the ³F₄, ³ H₅, and ³H₄ absorption bands of Tm³⁺. The calculated maximum slope efficiencies were determined to be ~40, ~57, and ~84%, respectively, for each of the ³F₄, ³H₅, and ³H ₄ absorption band pump schemes and the threshold pump power over the range of pump schemes was determined to vary by only 28%. The model was further used to analyze the fiber laser output when the fiber length, Tm³⁺ concentration and ³H₄ energy level lifetime were varied and the consequences on the operation of the fiber laser with these variations are discussed