Accelerated radiative emission from metallic nanocavity-embedded atom

Highly-accelerated and bright spontaneous emission is observed from Er atoms placed at the antinode of gold nano-trench cavity. Through time-resolved photoluminescence measurement, the average decay rate of Er atoms is enhanced by more than 100 times when compared to that located in a homogeneous silica matrix. We claim that over 50% of the photons coupled to the cavity is re-emitted into the free space, which implies the equivalent high quantum efficiency. The unambiguous confirmation of strong Purcell enhancement is attributed to the long radiation lifetime of Er atom and the very small modal volume of the metallic nano-cavity.