Collective radiation of multi-atom in cavity under the external driving field

Abstract There were several works concerning the collective radiation of two atoms in a cavity. According to their respective criteria, they all claim to have reached superradiation in a cavity (see paragraph 3 of the introduction for details). Dicke [1] defined that superradiation occurs when the radiation power of two atoms is greater than twice that of a single atom. We believe that this criterion is still valid when considering the radiation of atoms in the cavity. Here, we reexamine this topic and give a new but more reasonable criterion to test the collective radiation of multi atoms in the cavity. We tend to use the witness parameter W N as the criterion of superradiance. More importantly, as the frequency of the driving field is easy to adjust in the experiment, the radiation power of the atom in the cavity is calculated under the action of the coherent driving field, and the optimal frequency is given, that is, the single atom radiation and multi-atom radiation are enhanced at the same time. With such new criterion, we find it is impossible to get the superradiance in good cavity. On the contrary, superradiance is much easier to be reached in a bad cavity. We take the cases of one atom, two atoms, three atoms and four atoms for example. Anyway, the irradiation of atoms is non-classical whether it is subradiation or superradiation. The radiation power of the system can be significantly increased by simply increasing the number of atoms. These theoretical results can be realized by using the existing technology, which can make people understand the theory of multi-atom superradiance more clearly and stimulate future experiments.