  We study the scattering problem of photon and polariton in a one-dimensional
coupled-cavity system. Analytical approximate analysis and numerical simulation
show that a photon can stimulate the photon emission from a polariton through
polariton-photon collisions. This observation opens the possibility of
photon-stimulated transition from insulating to radiative phase in a
coupled-cavity QED system. Inversely, we also find that a polariton can be
generated by a two-photon Raman scattering process. This paves the way towards
single photon storage by the aid of atom-cavity interaction.
