Emission of an atom inside a one-dimensional atomic cavity

We study the emission of a single-photon by a two-level emitter inside an atomic cavity consisting of two atomic mirrors coupled to a one-dimensional waveguide. With proper atomic separations, we realize a frequency comb as well as spectrum narrowing in the waveguide with the symmetric setting, and also unidirectional spectrum narrowing with asymmetric parameters. Within a suitable range, we can control the central frequency of the narrowed spectra by modulating atomic separations. Due to the collective interaction among the emitters, entanglement sudden birth and revival are observed between the mirrors.