Most of the recent molecular cavity QED experiments, however, use the setup illustrated in Fig. , where many molecules are collectively coupled to the quantized electromagnetic field inside a Fabry-Pérot optical cavity (formed by reflecting mirrors). To describe this collective regime of light-matter coupling, the Tavis-Cummings (TC) model Hamiltonian is used as an analog to the JC Hamiltonian with many molecules. This model is under the same level of approximation (mainly the rotating wave approximation) as the JC model but with many molecules, taking the following form