“…For example the fluorescence of the three level atom in laser is a kind of noise, and we can control it by the following process. Also to illustrate more applications of three level atoms, we can consider the electromagnetically induced transparency (EIT) which was first observed in Strontium vapor [9] or the effect of strong depopulation of the initial state when considering the multiphoton population transfer and scattering of low-frequency light by a three-level system in the lambda-type configuration [10].…”