Abstract
In this study, two themes are investigated: “The Electromagnetically-Induced-Transparency (EIT) Spectrum in Hot Atoms,” and “The Phase Mismatch of Four-Wave Mixing (FWM) Processes in Cold Atoms.” First, EIT effect and their systematic types are introduced along with two equations, OBE and MSE, which are required for the subsequent theoretical calculation. Λ-type and Ladder-type systems are discussed qualitatively in regard to the properties and causes of EIT spectrum in both cold and hot atoms. By deriving a series of analytical formulas of important parameters that can be used to describe the curve behaviors, the role that each experimental parameter plays in the system is controlled, while at the same time a preliminary understanding of the difference between the hot- and cold-atom systems is acquired. The results have the potential to support the development of future experiments. Second, the process of FWM and the effect of phase mismatch in a double Λ system are preliminary presented. By employing the methods of modulation of optical density per unit length and analogy with periodically poled structure of “Quasi-phase matching technology,” a solution to compensating energy dissipation caused by phase mismatch is discovered.