Free-space light could power high-speed optical WiFi: Page 3 of 4

February 16, 2021 //By Jean-Pierre Joosting
Free-space light could power high-speed optical WiFi
Plasmonic speed enhancements previously constrained to nanoscale phenomena are replicated on macroscopic optical devices.

In the new paper, Mikkelsen and Andrew Traverso, a postdoctoral researcher working in her laboratory, brought a more purposeful and optimized design to a large-area plasmonic device. Silver nanocubes just 60 nanometers wide are spaced about 200 nanometers apart, covering 17% of the device's surface. These nanocubes sit just seven nanometers above a thin layer of silver, spaced by a coating of polymer that is jam-packed with four layers of fluorescent dye.

The nanocubes interact with the silver base in a way that enhances the photonic capabilities of the fluorescent dye, causing a 910-fold increase in the overall fluorescence and a 133-fold emission rate enhancement. The superfast antenna also can capture light from a 120-degree field of view and convert it to a directional source with a record-high overall efficiency of 30%.

"Plasmonic effects have always been known to lose a lot of efficiency over a large area," said Traverso. "But we've shown that you can take attractive ultrafast emission features of a nanoscale device and recreate it on a macroscopic scale. And our method is very easily transferrable to fabrication facilities. We can create these largescale plasmonic metasurfaces in under an hour with pipettes and Petri dishes, just simple liquid depositions on metal films.”

The overall effect of the demonstration is the ability to capture light from a large field of view and funnel it into a narrow cone without losing any speed. To move forward with this technology, researchers would need to piece several plasmonic devices together to cover a 360-degree field of view and once again include a separate interior detector. While there is work to be done, the researchers see a viable path forward.


Silver nanocubes spread out over the new device's entire surface. Whereas previous research has reported on individual cubes displaying improved properties, the new work showed these efficiency improvements can be achieved on a macroscopic scale. Image courtesy of Andrew Traverso, Duke University.


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