Applications: plasmonic couplers & lenses that could create 2D holograms or focus light at the nanoscale.
Wakes occur whenever something is traveling through a medium faster than the waves it creates – in the duck’s case water waves, in the plane’s case sonic booms.
While nothing travels faster than the speed of light in a vacuum, light isn’t always in a vacuum. It is possible for something to move faster than the phase velocity of light in a medium or material and generate a wake. The most famous example of this is Cherenkov radiation, wakes produced as electrical charges travel through liquids faster than the phase velocity of light, emitting a glowing blue wake. In this case Harvard researchers created similar wakes of light-like waves moving on #metallic surface = surface plasmons
Capasso’s team designed a faster-than-light running wave of charge along a 1D metamaterial – a nanostructure of rotated slits etched into a gold film, changes phase of the surface plasmons generated at each slit relative to each other, increasing #velocity of the running wave. The nanostructure also acts like the boat’s rudder, allowing steering
The angle of incidence of the light shining onto the metamaterial provides an additional measure of control and using polarized light can even reverse the direction of the wake relative to the running wave – like a wake traveling in the opposite direction of a boat.
“In order to view the wakes, we used an experimental technique that forces plasmons from the surface, collects them via fiber optics and records the image.”
http://www.eurekalert.org/pub_releases/2015-07/hu-saw070615.php
This is an artistic rendition of the superluminal running wave of charge that excites the surface plasmon wakes.
CREDIT
Daniel Wintz, Patrice Genevet, and Antonio Ambrosio.
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