The universal luminescence behavior of three-level system

The universal luminescence behavior of three-level system is studied. Through theoretical analysis, the population of each energy level under different pump powers could be obtained. Further, the power decay rate coefficient (kD) was proposed and analyzed. The kD represents the effect of the excitation pump power on the decay process of S2, and it is universal available either under weak or intense excitation powers. Besides, the population of S2 could be described by the ratio of kD to the total decay rate. The above analysis could be verified through the experiment.