Resonant Polariton Fluorescence in Gallium Arsenide

We present the first experimental study of $n=1\mathrm{}$ exciton-polariton fluorescence in a semi-conductor under resonant optical excitation. An order of magnitude enhancement of the radiative efficiency, a substantial narrowing of the fluorescence linewidth, and highly nonthermal energy distributions are observed at resonance. These new effects are interpreted in the polariton framework, stressing the dependence of polariton lifetime, damping, and escape time on energy and distance from crystal surface.