Rediscussion on longitudinally pumped quasi three level laser system

Taking into account that the laser upper and lower levels have different level lifetimes and that the natural decay of the upper level will affect the population of the lower level,the author revi ses the quasi three level model developed by Fan et al. Although the derived predictions are similar to those by Fan mathematically,the revised model is more appropriate to describe the lasing process.The theoretical calculations have a good aggreement with the experimental results.