  We report a theoretical study of the optical properties of a three-level
emitter embedded in an optical cavity including the non-rotating wave terms of
the light-matter interaction Hamiltonian. Rabi oscillations induced by a
continuous wave drive laser are responsible for a periodic time-modulation of
the effective cavity resonance, which results in a significant dynamical
Casimir emission. A clear signature of the back-action effect of the dynamical
Casimir emission onto the drive laser is visible as a sizable suppression of
its absorption.
