The spectral and temporal response of an optical cavity resonantly coupled to an ensemble of barium atoms has been investigated experimentally. The empty-cavity trnasmission resonances are found to split in the presence of the atoms and, under these conditions, the cavity’s temporal response is found to be oscillatory. These effects may be viewed as a manifestation of a vacuum-field Rabi splitting, or as a simple consequence of the linear absorption and dispersion of the intracavity atoms.

• Received 7 February 1990

DOI:https://doi.org/10.1103/PhysRevLett.64.2499