Title: Experiments with the multi-level atom-cavity system

Cavity QED is the study of interactions between atom and cavity field. Cavity modifies the emission properties of the atom, because of the collective strong coupling of the atom-cavity system, Vacuum Rabi Splitting of the atom-cavity system depends on . We are using this property for the state-dependent detection of multi-level systems. And we are also showing self-lasing in a driven strongly coupled atom-cavity system. This lasing behaviour is confirmed by the second-order correlation of the fluorescence output coming from the cavity.