  We investigate the dynamical Casimir effect and its detection with Rydberg
atoms. The photons are created in a resonant cavity with a plasma mirror of a
semiconductor slab which is irradiated by periodic laser pulses. The canonical
Hamiltonian is derived for the creation and annihilation operators showing the
explicit time-variation in the couplings, which originates from the external
configuration such as a nonstationary plasma mirror. The number of created
photons is evaluated as squeezing from the Heisenberg equations with the
Hamiltonian. Then, the detection of the photons as the atomic excitations is
examined through the atom-field interaction. Some consideration is made for a
feasible experimental realization with a semiconductor plasma mirror.
