Simulative investigation of the threshold characteristics of CW pumped four-level XPAL system

This paper presents a continuous wave exciplex pumped alkali laser (XPAL) four-level theoretical model ,which can simulate the pump threshold. The model is based on rate equation and calculated by the iterative algorithm. The pump threshold characteristics of CW pumped four-level XPAL system can be analyzed by this model. The analysis of the influences of temperature, the length of the vapor cell, linewidth of pumped laser, output coupler and the concentration of noble gas on pump threshold are presented. It is shown that there is an optimal temperature which will keep a low threshold. In addition, the analysis of the length of cell, output coupler, linewidth of pumped laser and the concentration of noble gas shows that the influence of the concentration of noble gas on the pump threshold is larger than other factors. Larger concentration of noble gas can increase the absorption of pump laser in gain medium.