  The transmission of a probe field experiencing electromagnetically induced
transparency and optical switching in an atomic medium enclosed in an optical
cavity is investigated. Using a semiclassical input-output theory for the
interaction between an ensemble of four-level atoms and three optical cavity
fields coupled to the same spatial cavity mode, we derive the steady-state
transmission spectra of the probe field and discuss the dynamics of the
intracavity field buildup. The analytical and numerical results are in good
agreement with recent experiments with ion Coulomb crystals [M. Albert et al.,
Nature Photon. 5, 633 (2011)].
