Optimization of the Efficiency of GaAs Saturable Absorber Q-switched Lasers

The laser efficiency is an important parameter, and we pay more attention to the maximum conversion efficiency of a laser in many cases. By taking into account the single-photon absorption (SPA) and two-photon absorption (TPA) processes of GaAs, the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density, and the pumping and the spontaneous emission during the pulse formation, the new normalized rate equations of a GaAs saturable absorber Q-switched laser are solved numerically, and the optimum laser efficiency of GaAs saturable absorber Q-switched laser is determined. A group of general curves are generated, which clearly show the dependence of the optimum laser efficiency on the parameters of the gain medium, the GaAs saturable absorber, and the resonator. In addition, the influence including the space variation, the pumping and the spontaneous emission is also shown. Sample calculations for a diode-pumped Nd³⁺:YVO₄ laser with a GaAs saturable absorber are presented to demonstrate the use of the curves and the relevant formulas.