  We explore the response of a quantum ring system coupled to a photon cavity
with a single mode when excited by a classical dipole field. We find that the
energy oscillates between the electronic and photonic components of the system.
The contribution of the linear and the quadratic terms in the vector potential
to the electron-photon interaction energy are of similar magnitude, but
opposite signs stressing the importance of retaining both in the model.
Furthermore, we find different Fourier spectra for the oscillations of the
center of charge and the oscillations of the mean photon number in time. The
Fourier spectra are compared to the spectrum of the many-body states and
selection rules discussed. In case of the center of charge oscillations, the
dipole matrix elements preselect the allowed Bohr frequencies of the
transitions, while for the oscillations of the mean photon number, the
difference of the photon content of the many-body states influences the
selection rules.
