Thermal model of continuous wave end-pumped passively Q-switched laser

A more accurate thermal model of continuous wave (cw) end-pumped passively Q-switched laser is established, by treating the absorption coefficient of the laser medium and the diffractive loss as a function of instantaneous population inversion density. The interactions between the transient temperature distribution in laser crystal and the output pulse parameters of cw-end-pumped passively Q-switched laser are investigated by numerically solving the coupling between the lasers rate equations and the transient heat conduction equation. The numerical results reveal that when the quasi-steady-state is reached, the instantaneous variations of the temperature in crystal and the absorption coefficient can result in the instability of the output pulse train in the passively Q-switched laser. Under the pump power of 5 W, the variation of output pulse amplitude reaches 0.5%.