Performance of continuously pumped, passively Q-switched, solid state lasers

This thesis studies the relationship between the pairs of resonator output coupling and intra-cavity absorber initial transmission, and the FWHM (full width at half maximum) pulse duration of a continuously pumped passively Q-switched solidstate laser, when the output energy is pre-determined. Depending on the magnitude of the pumping power, three different rate equation models are used to evaluate the required output coupler reflectivity and absorber initial-transmission pair for the corresponding FWHM pulse duration. The energy transfer kinetics of the passively Q-switched laser decides the required pumping power; and the pair of output coupler reflectivity absorber transmission pair, determine the build-up time of Q-switching and the repetition rate of the laser system. Hence, the forms of the models are controlled by two conditions: 1) the build-up time of Q-switching; and 2) the recovery time of the absorber. When the build-up time of Q-switching is relatively short, but the recovery time of the absorber is long, Model I is based on the simplified laser rate equations. It is used to evaluate the output coupler reflectivity and absorber initialtransmission pair, which satisfies the pre-determined output energy and FWHM pulse duration. Model II is set up to study the case when both the build-up time of Q-switching and the recovery time of the absorber are long. In Model II, the laser rate equations are solved using the Runge-Kutta method. Model III simulates the case when the recovery time of the absorber is short. To validate the models, the simulation results of practical passively Q-switched laser systems are compared with experimental results reported in the literature. The agreement of the simulation results with reported experimental results demonstrates the importance of the boundary conditions for the different cases, and verifies the soundness of the models. Generalizing the simulation results, obtained from different passively Q-switched laser systems with different pumping power and different pre-determined output energy, yields general conclusions which permit a designer to select the correct parameters for a desired laser performance.