Coherent Polariton Radiation and Light Localization

A system of resonance atoms is placed in a medium with developed polariton effect. In the spectrum of polariton states there can exist a band gap. If an atom with a resonance frequency inside the polariton gap is incorporated into the medium, the atomic spontaneous emission can be strongly suppressed. This is what is called the localization of light. Nevertheless, an ensemble of resonance atoms inside the polariton gap can radiate if their coherent interaction is sufficiently strong. Conditions when coherent polariton radiation can appear and the properties of this coherent polariton emission are studied.