Theoretical study on the laser performances of Nd^3+:YAG and Nd^3+:YVO4 under indirect and direct pumping

Based on the model of cw end-pumped four-level system, the laser performances of Nd3+:YAG and Nd3+:YVO4 under indirect and direct pumping Nd3+ ions into the upper laser level are compared. The model takes the effect of concentration-dependent fluorescence quenching into account and enables the optimization of Nd3+ lasers. The slope efficiencies for incident and absorbed pumping powers as well as the incident and absorbed pumping thresholds of Nd3+:YAG and Nd3+:YVO4 lasers under indirect and direct pumping are analyzed. When the slope efficiency for the incident pumping power and the incident pumping threshold are concerned, a simple criterion determining which sample is suitable for direct pumping is given; however, in the case of the slope efficiency for the absorbed pumping power and the absorbed pumping threshold, the direct pumping is always better than the indirect pumping.