Renaissance architects built into their cathedrals whispering galleries, circular chambers designed to amplify and direct sound waves so that, when standing in the right spot, a whisper could be heard from across the room. Scientists at the University of Pennsylvania have applied the same principle on the nanoscale to drastically reduce emission lifetime, a key property of semiconductors, which can lead to the development of new ultrafast photonic devices. The Penn team’s semiconductor nanowires can jump directly from a high-energy excited state to the ground, all but eliminating the cool-down period.At their core, the nanowires are cadmium sulfide, but they are also wrapped in a buffer layer of silicon dioxide and an outer layer of silver. The silver coating supports what are known as surface plasmons, unique waves that are a combination of oscillating metal electrons and of light. These surface plasmons are highly confined to the surface the silicon dioxide and silver layers meet.For certain nanowire sizes, the silver coating creates pockets of resonance and hence highly confined electromagnetic fields within the nanostructure. Emission lifetime can then be engineered by precisely controlling high intensity electromagnetic fields inside the light-emitting medium, which is the cadmium sulfide core.Learn more from the University of Pennsylvania.
Nanoplasmonic ‘Whispering Gallery’ Breaks Emission Time Record in Semiconductors
