We report experimental observation of two dynamical regimes in operation of a $\mathrm{Tm}:{\mathrm{YAlO}}_3$ microlaser: a stable continuous wave and robust self-pulsing. The experiment makes possible the assumption of exited-state absorption at the lasing wavelength. Such excited-state absorption can be a good candidate to explain the well-known instabilities observed in some thulium-doped lasers. Our rate equation model takes account of the phonon-assisted excited-state absorption ${}^3\mathrm{H}_5\to {}^3\mathrm{H}_4$, and the cross-relaxation and up-conversion processes. The results of numerical calculations are in good agreement with experiment.

• Received 9 February 2006

DOI:https://doi.org/10.1103/PhysRevA.73.053815