Microwave excited optical transparency enhancement resonances in Hanle-EIT configuration

We report an experimental observation of the optical transparency enhancement resonances in Hanle-electromagnetically induced transparency (EIT) configuration with a microwave field excitation. In this experimental system, a strong control field and a weak probe field form three-level A-type configurations of EIT. The fourth level is coupled by an additional microwave field. With the microwave field excitation, the probe field undergoes a process of absorption to transparency when the probe field decreases. Compared with the EIT effect, this result indicates optical transparency enhancement. A simple theoretical model and a numerical simulation are presented to explain the observed experimental results. The applications of these optical features are also discussed.