Cavity field spectra and entanglement in a three-level Jaynes-Cummings model with field damping

The effect of cavity leakage on cavity field spectrum and entanglement between the atom and field in a degenerate Lambda-type quantum-beat system containing a cavity of arbitrary Q is theoretically investigated by preparing the atom in the excited level and the cavity mode in vacuum. The number of spectral lines and spectral line widths depend on the splitting of lower atomic levels and cavity field decay rate as well as the passband width of filter. Spectral lines close to cavity frequency are mostly affected by damping. Spectral components at atomic transition frequencies have strong resistance against damping effect. Disentanglement periodically occurring in an ideal cavity is removed by field damping.