Fast and bright spontaneous emission of Er3þ ions in metallic nanocavity

By confining light in a small cavity, the spontaneous emission rate of an emitter can be controlled via the Purcell effect. However, while Purcell factors as large as B10,000 have been predicted, actual reported values were in the range of about 10–30 only, leaving a huge gap between theory and experiment. Here we report on enhanced 1.54-mm emission from Er3þ ions placed in a very small metallic cavity. Using a cavity designed to enhance the overall Purcell effect instead of a particular component, and by systematically investigating its photonic properties, we demonstrate an unambiguous Purcell factor that is as high as 170 at room temperature. We also observe 490 times increase in the far-field radiant flux, indicating that as much as 55 % of electromagnetic energy that was initially supplied to Er3þ ions in the cavity escape safely into the free space in just one to two optical cycles