This may look like a piece of abstract art, but you’re actually looking at the cutting-edge of optical technology. Using a branch of physics known as plasmonics, this microscopic set-up can pulse light on-and-off a bewildering 90 billion times per second.
The system is fairly straightforward, at least in theory. The square lump you can see is actually a nanocube just 75 nanometres across. Sat a mere 20 atoms beneath it is a thin sheet of gold, and between are scattered a series of spheres made of semiconducting material, each just six nanometres wide, known as quantum dots (the pink things in the picture above).
A team from the Pratt School of Engineering at Duk has shown that laser light pulsed onto the cube causes a series of excitations where light and free electrons combine to create what is known as a plasmon. Then, the accurate spacing between the cube and the gold sheet creates a field between the two which excites the quantum dots at incredibly high frequency — in this case, 90 gigahertz. That causes the quantum dots to emit light, pulsing on and off 90 billion times per second. The result is published in Nature Communications.
The team reckons that the ultra-high frequency of light emission could be used to create new kinds of ultra-fast light circuitry to transmit data. To make that a reality, though, will require a single quantum dot to be situated between the cube and the gold sheet to create a single photon source. Well, nobody said it was going to be easy.