Dynamics of a green upconversion-pumped Er:YAG laser exhibiting reabsorption losses

In this paper we model the dynamical behavior of a green-emitting upconversion-pumped Er(0.5 at.%):YAG laser, using the rate equations. An important peculiarity of this laser is the reabsorption of laser radiation by the parasitic 4I13/2→2H29/2 excited-state absorption process. This process represents a supplementary intensity-dependent loss mechanism that can, in certain conditions, produce self-pulsing behavior of the Er:YAG laser. Stability analysis is used to identify the various regimes of laser emission and the bifurcations leading to them. The results are illustrated by Runge-Kutta integration of the rate equations for values of control parameters corresponding to various laser emission regimes. The model can be applied for the prediction and enhancement of the performances of the green Er3+ upconversion lasers.