Polariton stark effect in dispersive and photonic band gap materials

The polariton stark effect has been studied in dispersive and photonic band gap materials doped with a two-level atom in the presence of a monochromatic driving laser field. The driven atom gets excited to the higher state and the system spontaneously decays to the ground state by emitting polaritons. The power spectrum of polaritons emitted by the atom is calculated by using the master equation for the density matrix in the presence of the damping. It is found that when the excitation frequency of the atom lies outside the energy gap and the Rabi frequency associated with the driving field becomes comparable to or larger than the atomic line width, the polaritons spontaneous decay spectrum splits into three peaks. We call this phenomena the stark effect. The central peak has a line width smaller than that of the two side peaks. Numerical calculations are performed for GaAs and SiC semiconductors