The Free Exciton in KI. I. Polariton Nature of the Emission

Abstract

The free exciton luminescence of KI is analysed in the polariton framework. The structure of the 0 L.O line and its L.O phonon replica can be explained by a spatial distribution effect, due to the fact that the polaritons are transformed into photons at the surface of the crystal with a probability function of their energy. The new very weak emission we detected at 6 eV is attributed to the upper branch polariton.