Theoretical investigation of quasi-three-level longitudinally pumped continuous wave lasers

A new theoretical derivation that makes it possible to compute the performance of a quasi-three-level longitudinally pumped cw laser is proposed. This theory, which takes into account the laser wave amplification and the pump wave absorption saturation coupling, seems simpler and more accurate than what has been previously published. The model accounts for single-pass, double-pass, and resonant pumping and can be used to characterize the thermal effect in the gain medium. It is also well suited for designing and optimizing such lasers. As an example, the theory is applied to the well-known Yb:YAG gain medium.