A Versatile Model for Temperature-Dependent Effects in Tm-Doped Silica Fiber Lasers

We have derived a model to provide a unique insight into the temperature-dependent effects in Tm-doped silica fiber lasers with consideration of important energy transfer processes and full spectra of laser transition. By fitting experimental measurements, the dependence of emission and absorption cross sections on temperature was characterized. With careful thermal management to control the influence of thermomechanical and thermooptical effects, a good agreement was achieved between simulations and experiments, even in the kilowatt power domain. On the basis of the model, the investigation shows that the thermal distribution of ions over the Stark sublevels contributes a higher threshold and a lower laser power as the temperature increase. Fortunately, this degradation of laser performance can be largely weakened when higher pump intensity is employed. The simulations also show that lower output coupling and longer operational wavelength can mitigate the output power variation arising from the temperature. The model was further used to analyze the dependence of laser spectrum on the fiber length and pump power when temperature changes. In addition, the laser output power and temperature distribution in kW-level are also studied.