Based on the model of cw end-pumped four-level system, the laser performances of
under indirect and direct pumping
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
lasers. The slope efficiencies for incident and absorbed pumping powers as well as the incident and absorbed pumping thresholds of
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.
© 2005 Optical Society of America